OBJECTIVE: To study the pelvic floor electromyographic (EMG) responses of a cohort of patients diagnosed with vulvar vestibulitis. STUDY DESIGN: Following full medical and laboratory workup, patients with vestibulitis were given pelvic floor EMG. Results were compared with the collated data, termed the ''nonmorbid EMG pelvic floor response, '' derived from a study control group of 50 symptomless subjects. Six aspects of the EMG response were examined: resting baseline, contractile potential, resting standard deviation, recruitment, recruitment recovery and power spectral analysis. RESULTS: As compared to the study control group, the cohort demonstrated elevated vesting baseline above 2.0 mu V) in 23 (71%); poor contractile potential, < 17 mu V, in 20 (65%); elevated resting standard deviation, > 0.20, in 30 (93%); slow to poor recruitment recovery after contraction, greater than or equal to 0.2 seconds in 27 (86%) and low frequency, < 115 Hz in 22 (69%). CONCLUSION: The study confirmed that of vestibulitis patients, 88% will show at least three of the above altered criteria and that the diagnosis can be confirmed by: (1) the instability of muscle, (2) poor muscle recovery after contraction, and (3) elevated resting baseline plus one other optional criterion, either (4) reduced frequency or (5) reduced muscle contraction strength.