This report describes an intravaginal balloon device (IVBD) and an improved method for measuring the dynamic characteristics of circumvaginal muscle (CVM) contractions. The IVBD measurement system may be used in research on women's health problems related to the pelvic floor musculature. The system is independent of examiner judgment and variability, and measurement conditions are carefully controlled. In an initial trial using the device with 20 volunteers, aged 22 to 58 years, the maximal pressure developed during strong CVM contractions was measured with the subjects supine. Subjects were asked to repeat the contraction while they contracted abdominal muscles. The length of time a submaximal contraction could be held was also measured. Test-retest reliability, determined by repeating each experiment, revealed significant correlation in maximal pressure attained, r = .85, p < .03. A t test demonstrated no significant difference between the variables with and without the use of abdominal muscles, indicating the contraction of abdominal muscles did not affect intravaginal pressure when assessed with the IVBD. A weak correlation between length of time a submaximal contraction could be held and age of subject was found, r = -.44, p < .06, but no pressure variable was correlated with age or parity, a possible effect of the small sample in this study.