BACKGROUND: This study was undertaken to determine the prevalence of psychiatric disorders in infertile women and men undergoing in vitro fertilization (IVF) treatment. METHODS: Participants were 1090 consecutive women and men, 545 couples, attending a fertility clinic in Sweden during a two-year period. The Primary Care Evaluation of Mental Disorders (PRIME-MD), based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edn (DSM-IV), was used as the diagnostic tool for evaluating mood and anxiety disorders. RESULTS: Overall, 862 (79.1%) subjects filled in the PRIME-MD patient questionnaire. Any psychiatric diagnosis was present in 30.8% of females and in 10.2% of males in the study sample. Any mood disorder was present in 26.2% of females and 9.2% of males. Major depression was the most common mood disorder, prevalent in 10.9% of females and 5.1% of males. Any anxiety disorder was encountered in 14.8% of females and 4.9% males. Only 21% of the subjects with a psychiatric disorder according to DSM-IV received some form of treatment. CONCLUSIONS: Mood disorders are common in both women and men undergoing IVF treatment. The majority of subjects with a psychiatric disorder were undiagnosed and untreated.