This retrospective survey aims at describing patients subjected to prefrontal lobotomies and the general treatment conditions at Umedalen State Mental Hospital during the period 1947-1958. Data collected from psychiatric and surgical medical records was analysed using quantitative and qualitative content analysis. A total of 771 patients subjected to lobotomy during the years 1947-1958 were identified. From these, a sample of 105 patients was selected for the purpose of obtaining detailed data on socio-economic status, diagnosis, symptomatology, other psychiatric treatments applied before the pre-frontal lobotomy operation, time spent in hospital before operation, praxis of consent and mortality. The diagnosis of schizophrenia was found in 84% of the 771 lobotomized patients. The post-operative mortality was 7.4% (57 deaths), with the highest rate in 1949 (17%). The mean age of the patient at the time of operation was 44.8 years for females and 39.5 years for male patients. The average length of pre-operative time in hospital for females was 10.7 years and for males 3.5 years. It remains unclear why this mental hospital conducted the lobotomy operation to such a comparatively great extent. Factors such as overcrowding of wards and its status as a modern mental hospital may have contributed.