A single-blind prospective randomized controlled trial was carried out to determine the utility of pelvic floor exercises in nulliparous women without dysfunction. Thirty-five nulliparous women without clinical evidence of pelvic floor dysfunction were recruited via newspaper advertisements. Twenty-four subjects completed the study at the Clinical Research Unit of the University of North Carolina Hospitals. Subjects were randomly assigned to either 6 weeks of pelvic floor (Kegel) exercises or their usual activities. The main outcome measures were vaginal and rectal electrical activity by surface electromyography with acrylic plug electrodes, and circumvaginal strength rating by digital examination. The outcome observer was blinded to group assignment. No improvement was found in either electrical activity or digital strength assessment. The differences between treatment group and control group between sessions with 95% confidence intervals were: total strength -0.5 (-2.39, 1.39), rectal flick 3.3 (-1.67, 8.22), rectal hold 1.7 (-0.96, 4.38), vaginal flick 0.5 (-3.17, 4.16), and vaginal hold -0.9 (-3.96, 2.25). It was concluded that pelvic floor exercises were ineffective in a group of nulliparous women without clinical dysfunction. Power to accept the null hypothesis is small, but perusal of the confidence limits between sessions cast some doubt on the efficacy of this intervention.