The effects of low-estrogen and progestogen-only contraceptives on blood pressure changes were investigated on 238 women taking 35 micrograms EE OC, 267 using Norplant implants and 259 adopting IUD. The mean increases in diastolic pressure at 12, 24, 36 and 48 weeks among pill users were significantly (p < 0.05) higher than those among IUD users by 1.8, 2.1, 2.3 and 1.9 mm Hg, respectively; the increases in systolic pressure were higher but not significant (p>> 0.05) by 1.3, 1.7, 1.5 and 1.3 mm Hg. Neither systolic nor diastolic blood pressure was affected by use of Norplant implants. Regression analysis, including interaction terms, showed that women's age, obesity and family history of hypertension were associated with an increase of blood pressure during follow-up and were independent of contraceptive use and vice versa. After adjustment of some potential confounding variables, pill users showed a 1.0 mm Hg rise in diastolic pressure, which is statistically significant but clinically unimportant.