Soluble fibrin monomer complexes (SFMC) were determined in users of different oral contraceptives. Quantitative gel filtration of beta-alanin precipitated plasma samples yielded the relative (per cent of total fibrinogen content) and absolute (mg per 100 ml plasma) amount of SFMC. Increased levels of SFMC were observed in users of oral contraceptives, when compared to age, parity and socioeconomic background matched control groups. This increase was more pronounced in users of Neogynon (0.05 mg ethinyl estradiol, 0.25 mg norgestrel) than in the one using Microgynon (0.03 mg ethinyl estradiol, 0.15 mg norgestrel). Users of Ovulen (0.1 mg mestranol, 1 mg ethynodiol diacetate) in addition to the rise of SFMC levels exhibited elevated fibrinogen levels in plasma. The data presented indicate a limited state of hypercoagulability in users of oral contraceptives.