Professor Manfred Frey started his scientific career in 1974 at the Institute for Topographic Anatomy at the University of Vienna where, besides his teaching tasks in anatomy classes, he worked on an experimental project for clarifying the role of afferent propioceptic nerve fibres for muscle trophism. Upon his relocation to the Second University Clinic for Surgery Vienna, this also built a bridge to the scientific activities there. Reconstruction of the neuromuscular system, and in particular muscle transplantation for replacing definitively lost muscle function, had been a long-standing key subject for the team of researchers in the department for plastic and reconstructive surgery. The projects conducted by Prof. Frey were dedicated to optimizing the nerve supply of muscle transplants, to clarifying the factors influencing the functional result of muscle transplants, and to comparing free muscle transplantations with and without microsurgical reconstruction of the vascular supply. Clinical studies were dedicated to the application of fibrin glue in skin transplants, free microsurgical tissue transfers, hand surgery concerning flexor tendon sutures, replantation surgery and sensomotorically differentiated nerve suture of peripheral nerves. Microsurgical reanimation of the paralyzed face has been an important scientific subject right from the start. A number of other experimental and clinical studies were aimed at mobilizing paraplegic patients with functional electro-stimulation, and the use of electro-stimulated skeletal muscles for improving the pumping capacity of insufficient heart muscles (cardiomyoplasty). The subject of the state doctorate in surgery with a particular focus on plastic and reconstructive surgery in 1984 was "Free functional muscle transplantation".

Following his appointment to C-3 professor for hand and microsurgery at the medical faculty of RWTH University Aachen in 1987, the research was focused on hand surgery topics, but also muscle transplantation and cardiomyoplasty again. Subjects to do with the treatment of burns came to play an increasingly important part in keeping with the focus area of the clinic.

Appointment as senior physician for general plastic surgery at University Hospital Zurich one year later was soon followed by a renewed habilitation at the medical faculty of the University of Zurich in the subject of "cardiomyoplasty". Nomination as associate professor at the University of Zurich in 1995. The experimental muscle transplantation studies were continued in Zurich, where a new experimental model for transplanting a 1 g mimetic muscle with microneurovascular anastomoses was described by Prof. Frey for the very first time, and numerous details of muscle transplantation into the paralyzed face were clarified. The innovative surgical procedure of end-to-side nerve suture was taken up clinically and experimentally, important technical details of the surgery clarified, and the clinical suitability of this surgical procedure established. Multi-centric studies concerning neuromuscular reconstruction of the paralyzed face could be intensified by establishing an international study centre in Zurich. An important contribution to this was the development of a completely new measuring method for objectivizing facial movements by 3D video analysis. Several clinical studies were dedicated to breast surgery, a new breast reduction procedure was developed by Prof. Frey, and the immediate reconstruction of the female breast after breast removal because of breast cancer introduced. Studies into the psychosocial environment of patients during plastic surgery treatment of facial paralysis and/or breast reconstruction were also started in Zurich.

After 9 years of working at universities abroad, Professor Frey was appointed professor for plastic surgery at the Medical University of Vienna, and hence simultaneously took on the management of the clinical department for plastic and reconstructive surgery at Vienna General Hospital - New University Hospitals. A movement analysis laboratory was established as part of his appointment. The "International Registry for Neuromuscular Reconstruction in the Face“ was centralized in Vienna. The previous focus areas of the research were developed further clinically as well as experimentally, while a number of new ones were added on the basis of research collaborations and/or because of topicality.

Prof. Frey is also continuing his scientific activities after retiring from his job at the Medical University of Vienna. This in particular concerns his research focus on reanimating the paralyzed face, in which respect he has provided suitable conditions for clinical top-level research with international networking by establishing the "International Center for Facial Nerve Surgery".

A current list of ongoing research projects:
- Free functional muscle transplantation
- Nerve regeneration, motor and sensory reinnervation
- End-to-side nerve suture
- Microsurgical reanimation of the paralyzed face
- 3D video analysis of facial movements
- International multi-centre study "Neuromuscular reconstruction in the face"
- Psychosocial environment of patients with facial paralysis
- Thought-controlled arm prosthesis
- Breast reconstruction breast cancer patients
- Nationwide breast reconstruction study in Austria
- Psychosocial environment of breast reconstruction patients in connection with breast cancer
- Reconstruction for malignant tumours of the soft tissues
- Objektivization of results in aesthetic surgery (breast reduction and breast lift; influence of facelifts on facial expressions)