Aims: The aim was to study whether sick-leave diagnoses of long-term sickness absentees were modified after a multidisciplinary assessment and if modifications differed with type of medical specialty of the latest physician to sick-list the patient. Methods: A sample of 635 long-term sickness absentees referred to a multidisciplinary assessment by Social Insurance Offices was included. Data were obtained through sickness certificates and medical records. Patients were examined by board-certified specialists in psychiatry, orthopaedic surgery, and rehabilitation medicine. Descriptive statistics were used. Results: The multidisciplinary assessment resulted in an increase from 1—2 to 2—3 diagnoses for most patients. Forty-five per cent of the male and 47% of the female patients had only somatic diagnoses at referral. After the multidisciplinary assessment these percentages were 20% and 29%, respectively. The rate of women and men given both psychiatric and somatic diagnoses increased from 30% at referral to about 55%. The shift from either only psychiatric or only somatic diagnoses to having these diagnoses in combination was associated with type of specialty of the physician who had sick-listed the patient. Conclusions: The study indicates that many patients on long-term sick-leave with unclear diagnoses may suffer from unrecognized, and therefore probably untreated, medical disorders and co-morbidity.