Background This research examines the physical health of patients with severe, chronic obsessive-compulsive disorder (OCD) and compares the findings with patients admitted to an acute general psychiatric ward. Methods Successive admissions to a specialist inpatient unit treating patients with OCD were included in the study. Information including gender, age, weight and height were recorded along with the results of blood tests for urea, liver function tests and blood lipids. In addition, type and dose of medication were also recorded. These data were compared with information obtained via the case records from successive admissions to a general psychiatric ward. Results A total of 104 patients with OCD and 101 patients admitted to an acute psychiatric unit were studied. OCD patients were generally younger than the controls and were on a lower dose of antipsychotic medication. Despite this, the OCD patients were more likely than the general psychiatric patients to have raised blood lipids. Raised creatinine was also more common among OCD patients. Conclusion The study demonstrates that patients with severe OCD have significant evidence of serious physical health problems.