African men play important roles in the decisions about family life, including fertility and family planning. However, fertility and family planning research and programmes have ignored their roles in the past, focusing only on women's behaviours. Since the 1994 International Conference on Population and Development (ICPD), interest in men's involvement in reproductive health has increased. Unfortunately, data on their knowledge and use of contraception are generally scanty. This paper examines knowledge and use of contraception among ever-married men in Nigeria. A total of 1451 ever-married men aged 18-55 were interviewed in Imo and Ondo States, Nigeria. The findings reveal that men's level of contraceptive knowledge is high in the study areas. About 90% knew at least one method of family planning. Furthermore, the level of contraceptive use among married men is such that men could participate in family planning activities if there were adequate programmes to involve them. Men in the sample areas were found not only to support their spouses' use of contraceptives, but were actually using condoms to delay or prevent pregnancy. Age, education, place of residence, number of living children and being counselled for family planning were identified as key factors determining contraceptive knowledge and use among married men in the study areas. To ensure increased participation of men in family planning, programmes must be designed to educate them on the need for family size limitation and involve them in service delivery, even if only to their male counterparts.