OBJECTIVE: To explore the pulsatile-release characteristics of LH and P in women with premenstrual syndrome (PMS) compared with age-matched phase-matched controls. DESIGN: Prospective, repeated measures, two-group study. SETTING: Human volunteers in an academic research environment. PARTICIPANTS: Six women with rigorously defined prospectively determined PMS; six age-matched phase-matched controls. MAIN OUTCOME MEASURES: Frequency, amplitude, concentration, and coincident pulsatile release characteristics of LH and P at three symptom-related points of the luteal phase. RESULTS: No significant between-group differences in frequency, amplitude, or concentration were found. In pooled data, significant coincident pulsing between LH and P was demonstrated. The length of time between LH and P pulses systematically increased across the luteal phase, a finding not previously reported. In the PMS group only, significant coincident pulsing occurred at an unexpected zero time lag on the symptom-onset sampling day. CONCLUSION: A progressively increasing coupling interval may reflect the gradual decline of the corpus luteum. Presence of a zero time lag between LH and P at symptom onset in women with PMS may indicate an aberrance in corpus luteum response to LH stimulation.