OBJECTIVE Verapamil has been associated with hyperprolactinaemia, but there have been no population‐based studies. Our objective was to determine the prevalence and degree of hyperprolactinaemia associated with verapamil in the clinical setting.DESIGN Observation with cross‐sectional and longitudinal components in the setting of an urban teaching hospital and its satellite out‐patient clinics.PATIENTS Male out‐patients excluding those taking other drugs known to raise PRL, renal failure and known primary hypothyroidism (1265 eligible subjects). Control subjects were drawn from eligible out‐patients not taking verapamil.MEASUREMENTS Serum PRL levels, frequency of persistent hyperprolactinaemia and total testosterone levels.RESULTS Prolactin levels were obtained in 449 subjects on verapamil (35.5% response rate) and 166 controls. The proportions of individuals with hyperprolactinaemia (PRL> 460 mU/l) were 0.085 and 0.030 in the verapamil and control groups, respectively (P = 0.012, χ2‐test). The mean (±SD) serum PRL levels were 267 ± 205 and 203 ±118 mU/l in the verapamil and control groups, respectively (P  120,P < 0.00001). The ± SD serum testosterone levels at follow‐up were significantly lower in Group 1 (6.16 ± 2.52 nmol/l) than in Group 2 (9.42 ± 3.92 nmol/l,P = 0.029, independentt‐test).CONCLUSIONS The prevalence of hyperprolactinaemia associated with verapamil use in this study of male out‐patients was .5% (95% Cl 5.9–11.1%). The persistence of hyperprolactinaemia when verapamil was continued (Group 1) and the return to normal PRL levels when verapamil was discontinued (Group 2) confirm verapamil’s causal role in the development of hyperprolactinaemia. While low testosterone levels were common in both groups, testosterone levels were lower in patients on verapamil. Our data suggest tha