Endemic trial biopsies were obtained on postabortal days 1 to 36* in '12 women without contraception, in 28 women using oral contraceptives, and in 12 women with intramerine devices. Tissue samples were examined for day-today sequential changes, specifically: a) regenerative, repair, proliferative and secretory activity, b) involution of pregnancy changes, c) inflammation. In the absence of contraception, the endometrium promptly regenerated. The earliest evidence of ovulation was on day 9. One-third of the women ovulated before the first period. Incomplete placental and decidual involution was seen in *15% of patients, but its frequency progressively decreased toward the end of observation. Inflammation seen in 26% was limited to the retained decidua and was, therefore, thought to be a reactive rather than an infectious phenomenon. In women taking oral contraceptives, initial regeneration was also prompt. “On pill” changes resembled the nonpostabortal picture except for a few-cases of cystic glandular dilation, or Arias-Stella-like phenomena. Retained decidua and inflammation were more frequent (75% and 689c) than m the noncontraceptive group, and the diminishing trend was not observed. In the iutrauterine device group, inflammation was more frequent (83%) than in the other two groups and was not limited to the decidua.