Objectives: This study assessed the importance of the Traditional Chinese Medicine (TCM) pattern on an acupoint-specific effect. Design: This was a TCM pattern subdivision analysis of the first intervention data from a multicenter, randomized, controlled trial (ISRCTN24863192) (the main trial). Settings: The main trial recruited participants from six hospitals in three provinces in China. Subjects: Five hundred and one (501) participants diagnosed with primary dysmenorrhea (PD) were enrolled in the main trial. Interventions: The main trial randomly and equally divided participants into three treatment groups with bilateral electroacupuncture at three sites, respectively: Sanyinjiao (SP6), Xuanzhong (GB39), and an adjacent nonacupoint. Participants were diagnosed with TCM patterns before the treatment. The intervention was carried out when the visual analogue scale (VAS) score of participant's menstrual pain was >= 40 mm on the first day of menstruation and lasted for 30 minutes. Outcome measures: The immediate improvement of pain was measured with a 100-mm VAS before the intervention, at 5 minutes, 10 minutes, and 30 minutes during the intervention, and at 30 minutes after the completion of this intervention. Results: Three (3) TCM patterns (n = 320) were eligible for analysis, including Cold and Dampness Stagnation pattern (n = 184), Qi and Blood Stagnation pattern (n = 84), and Qi and Blood Deficiency pattern (n = 52). In Cold and Dampness Stagnation pattern, the SP6 group had a significant reduction in VAS scores compared with the GB39 group (mean difference -7.6mm) and the nonacupoint group (mean difference -8.2 mm), respectively. There was no difference between the latter two groups. There were no group differences in VAS scores in the other two patterns. Conclusions: It suggested that TCM pattern might affect acupoint specific effect on the immediate pain relief obtained for participants with PD.