Infant and child health and nutrition education messages patterned after the reach-and-frequency technique of commercial advertising were broadcast to target groups of young mothers over local radio stations in the Philippines and Nicaragua for one year without the support of more conventional education methods. The messages were developed in consultation with local health and nutrition authorities, recorded using professional talent from local radio stations, pre-tested with representatives of the target audience, and aired according to the listening habits of the target groups. Evaluation data were gathered through questionnaires administered to mothers in their homes in baseline studies, six months after broadcasts began, and 12 months after the baseline. One thousand young mothers were interviewed in each wave of the interviews. Interviews were supplemented by self-administered questionnaires to doctors, teachers, and other community workers. Results indicated that the broadcasting was successful in improving practices of infant and child health and nutrition care. The reach-and-frequency technique provided a discipline that renders broadcasting to unorganized audiences--the most inexpensive use of radio--effective in bringing about changes in behavior, as well as attitudes and knowledge. Appendices include a household questionnaire, a questionnaire to community workers, a message test questionnaire, a letter to community workers, and examples of the actual radio messages. (Author/CMV)