We evaluated the variability and circadian changes in consecutive measurements of home uroflowmetry in 32 patients with symptomatic benign prostatic hyperplasia (BPH) and 16 healthy men. In the BPH group 476 uroflow measurements were recorded during 24 to 72 hours (mean 14.9 measurements per patient), and the controls produced 100 flow recordings (mean 6.25 measurements per participant). Great variability between consecutive peak flow rates was observed in the BPH group, ranging from at least 1 standard deviation in 28 of 32 patients (87.5%) to at least 2 standard deviations in 15 of 32 (47%). In 21 of 32 patients (65.6%) the highest recorded peak flow rate was greater than, while the lowest peak flow rate was less than the -2 standard deviations plot in voiding nomograms. In the control group variability between consecutive voiding episodes also was marked, namely at least 1 standard deviation in 8 of 16 men (50.0%) and at least 2 standard deviations in 2 of 16 (12.5%). However, in none of the control men was any peak flow rate measurement less than the -2 standard deviations line. Circadian changes in diurnal and nocturnal measurements of voided volume, interval to maximal flow, flow time, peak flow rate and adjusted peak flow rate were recorded in the BPH group, providing a urodynamic support to a well known clinical observation.