Patients in a private practice. evaluated for prostatism due to benign prostatic hypertrophy were offered the options of medical treatment with the alpha blocker terazosin, surgical treatment, or continued observation. Nineteen men accepted terazosin treatment and are the subjects of the present series. They were treated over a mean period of 8 months, the longest treatment lasting over 22 months. Dosage was started at I mgld and increased as tolerated to 2. 5 . and 10 mgld over the test period. Extensive testing including invasive urodynamics, multiple voiding diaries. and symptoms scores at each dosage level was carried out. We found that flow rates increased moderately from baseline in a dose dependent fashion. At the 10 mgld dosage some patients achieved flow rates in the low normal range. Patients on treatment documented a decrease in the number of voidings per day, a decrease in ntxturia, an increase in bladder capacity and the volume of each voiding. On the other hand. patients frequently did not appreciate changes in their voiding patterns. as refJected in their responses to the symptom questionnaires. We could not demonstrate significant changes in bladdcr pressures on cystometry either during filling or voiding. Our data suggested that terazosin may well have a direct effect on the fundus of the aging bladder to increase capacity. and, through the well-known relationship between voided volume and flow rate. increase urinary flow rate. ci? IW4 WIICY-LISS. Inc