Background: Physical distress resulting from medical problems has been found to cause increased behaviour problems in patients with intellectual disabilities (ID). Despite this fact, little has been documented on the medical problems of individuals with ID admitted for inpatient psychiatric care. We conducted an exploratory investigation based on a retrospective chart review of the medical problems and medications for 198 people with ID who had been admitted to a specialised inpatient psychiatric unit. Most patients were referred for admission because of aggressive, disruptive and self-injurious behaviours. The average length of stay was 17.6 days. Methods: We tallied the total number of medical problems and medications listed in the patients' discharge summaries. Because longer stays are disruptive, costly and associated with greater overall impairment, we examined the relationship between length of stay and frequency of discharge medical diagnoses. We also assessed whether or not the number of psychoactive medications correlated with the number of medical diagnoses. The effects of other demographic and diagnostic variables on rates of medical diagnoses and medications were also evaluated, including gender, age group (16-25, 26-45, 46-60, greater than 60), level of ID (mild, moderate or severe ID) and diagnosis of an autism spectrum disorder or Down syndrome (DS). Results: Inpatients with a higher number of medical diagnoses had longer lengths of stay (Spearman r = +0.32, P less than 0.0001). There was a significant correlation between number of psychoactive medications and number of medical problems (Spearman r = +0.32, P less than 0.0001). The most frequent medical comorbidity was constipation, reported in 60% of the inpatients (n = 118), while gastro-esophageal reflux disease was identified in 38% (n = 75). Older inpatients had an increased number of medical problems, as might be expected, but a diagnosis of an autism spectrum disorder, gender and level of ID had no detectible effect on rates of either medical diagnoses or medications. There were only 13 inpatients with DS; in this modest sample, it was found that they had higher rates of osteoarthritis, cardiac problems, hearing loss, hypothyroidism and sleep apnoea than peers without DS, as is consistent with previous findings on overrepresented conditions in this trisomy. Conclusions: In the present study, individuals with ID admitted for inpatient psychiatric care exhibited high rates of medical problems, and these were associated with duration of inpatient stay. Based on these findings, further investigation of the effects of medical problems on behaviour among individuals with ID admitted for inpatient psychiatric care is warranted.