We had expected that cholesterol levels would be higher than the national average in this population of hospitalized psychiatric patients, given the large proportion taking antipsychotic medications. We were surprised to find that cholesterol values for inpatients were significantly lower than the national norm, and in most hospitals, rates were less than half that seen in the adult general population. We therefore commenced investigations to verify data accuracy, including verifying the chain of possession of blood samples and confirming the accuracy of laboratory processes. In addition, we examined how patients' cholesterol levels varied by age, because an inpatient population younger than the national average might account for the difference. However, we found no significant difference in cholesterol levels across inpatient age groups. Another possible reason for lower-than-expected cholesterol levels is exposure of these inpatients to interventions that may be more likely to occur in an inpatient setting than in the general population, including healthy diets, prescription of statins, and adherence to prescribed statins. Given the number of the hospitals involved and the geographic diversity of the patients, the results appear unlikely to stem from local variations in diet or prescribing practices. Rather, it appears that inpatient stays, many of which last several months or more, offer some protection from the elevated cholesterol so prevalent in the United States.