Hyperprolactinaemia is a common finding in patients treated with antipsychotics. A complete cohort of 194 schizophrenia and bipolar disorder patients receiving antipsychotics in a single community mental health trust in Halifax UK underwent routine prolactin screening in the absence of any reLevant symptomatoLogy. Values above the upper limit of normal were measured in 38% of the cohort and were more common in females (52%) than males (26%). Significantly elevated levels (>1000 mIU/l) were measured in 21% of the cohort. Risperidone monotherapy treatment was associated with hyperprolactinaemia in 69% of patients ( n = 35) and in 100% of female patients (n = 16) and amisulpride monotherapy in 100% (n = 7). Prolactin screening is not currently undertaken routinely in the UK. These data give some indication of prevalence of varying degrees of hyperproLactinaemia that might be found when screening an asymptomatic cohort of schizophrenia and bipolar outpatients. Clinicians may be helped by the reporting of such categorical data from clinical trials in addition to mean cohort values of prolactin. Long-term hyperprolactinaemia may be associated with clinical sequeLae in some patients.