A case-control analysis of hospital-based data was conducted to evaluate whether low-dose combination oral contraceptives (OCs) protect against pelvic inflammatory disease (PID). Other categories of combination OCs based on estrogen dose were also assessed. The results indicate no OC confers protection if taken for < 12 months. In contrast, the education-adjusted relative risk (RR) estimates for continuous exposure of ≥ 12 months for various categories of combination OCs based on estrogen dose all ranged from 0.2 to 0.4 with overlapping 95% confidence intervals (CIs); however, the adjusted RR for low-dose pills was not statistically significant (RR = 0.4,95% CI: 0.2,1.1). These data are consistent with the hypothesis that low-dose estrogen pills as well as higher dose estrogen OCs potentially protect against PID requiring hospitalization. Low-dose estrogen combination OCs deserve further study in relation to PID generally, and more particularly, in regard to specific microorganisms causing PID.