PIP: An analysis of the attitudes of Colombian women towards contraceptive use and actual contraceptive behavior indicates that knowledge of contraceptive techniques and access to supplies is critical to contraceptive use. Whether fertility can be significantly lowered without the prior occurrence of modernization has been questioned. In order to discover if there is motivation for family planning in Colombia, a developing country, independent of modernization, the results are examined of the National Fertility Study conducted in 1969 by the Colombian Association of Medical Faculties as a collaborative project with the Program of Comparative Fertility Studies in Colombia. 2951 married women or women living in consensual union in urban and rural areas were interviewed. Findings indicate that modern women, those of higher socioeconomic status, higher levels of schooling and of urban residence, are more likely to use fertility control methods and have fewer children. However, further analysis indicates that a favorable attitude toward family planning is independent of contraceptive use and that knowledge of contraception is strongly related to modernism and contraceptive use. Because urban women are generally more knowledgeable than rural women about all methods of contraception and the percent of all women claiming knowledge of each method increased with schooling level, lack of contraceptive knowledge rather than modernism is proposed as a critical factor in failure to practice birth control. In addition, traditional women are shown to be as likely as modern women to use contraceptive methods which did not require supplies and less likely to use those requiring technical knowledge. Consequently, cost and accessibility appear to be critical factors in contraceptive use. This demonstration that inadequate knowledge of birth control methods or restricted access to contraceptive supplies was probably more responsible for the limited practice of birth control in Colombia than were motivational factors associated with modernism would appear to keep open the possibility that widespread contraceptive practice can be achieved without modernizing the entire society.