The problem of premature unfitness for work of (grammar school) teachers is of great social and social-medical interest. The possible causes and suitable measures of intervention remain a subject of controversy. The aim of this study was, on the basis of a random sample of a large number of cases, to gain a differentiated overview of the extent and type of early retirement due to illness of grammar school teachers, in order to be able to develop evidence-based strategies for prevention and intervention. In a prospective evaluation, all the assessments of illness-related unfitness for work drawn up for civil servants and teachers between 1.1.1996 and 31.12.1999 in Bavaria were first of all systematically evaluated. In addition, from the total collective a subgroup was formed of grammar school teachers and this was analysed separately. The answers given in a standardized, anonymous questionnaire provided the database. The evaluation included e.g. socio-demographic and occupational factors, the morbidity spectrum, medical judgement, medical rehabilitation and evaluation of performance. The medical diagnoses of the main and accompanying illnesses were classified according to ICD 10 in organ-related groups. Evaluation was carried out by means of descriptive statistics. Of the 655 grammar school teachers assessed, 65% (n = 429) were men, 35% (n = 226) women. The median age for male teachers was 58 years old (range: 30-64 years old), for female teachers 55 years old (range: 32-63 years old). Previous conflicts at the school workplace were reported in 12% of the cases. Among the main medical diagnoses, psychic/psychosomatic complaints (41%) predominated over muscular/skeletal illnesses (14%) and cardio-vascular diseases (12%). 80% of those examined were judged unfit for work. 56% of the grammar school teachers had participated in at least one medical rehabilitation measure before the proceedings for determining unfitness for work were instigated. Psychic and psychosomatic illnesses took first place among the decisive complaints leading to early retirement, and made up 45% of these. Further differentiation revealed the predominance of depressive illnesses and exhaustion (burnout). The main somatic complaints were far less common: muscular/skeletal illnesses (13%), cardio-vascular diseases (12%) and malignant growths (8%). The performance of 70% of the grammar school teachers judged unfit for work was regarded as so severely reduced that even activity outside of the teaching profession was no longer feasible. In this first representative evaluation of illness-related early retirement in grammar school teachers, the high prevalence and great social-medical importance of psychic and psychosomatic illnesses is noteworthy. In Bavaria, almost every second grammar school teacher therefore becomes unfit for work as a result of such complaints long before they reach the normal retiring age. From a social-medical and occupational-medical point of view, there is urgent need for further research into potential illness-inducing occupational and non-occupational stress factors and the development and implementation of effective and efficient strategies for prevention and intervention.