The Growth and Development Monitoring Programme is a longstanding early childhood social intervention in Colombia. The programme's goal is the prevention and early identification of problems affecting children’s health and nutrition. To achieve this aim, the programme’s basic strategy is to educate parents about the overall health care of infants. The objective of this study is to measure the impact of this programme on children’s nutrition and health status and maternal child-care practices. To address potential selection bias, we employ quasi-experimental techniques. This article uses data from the Demographic Health Survey of 2010. The evidence suggests that the programme improved immunization status and the likelihood of health care for acute respiratory infection or fever. As expected, the programme has a greater impact on children from among the poorest people in the country. In the most advanced regions and for the beneficiaries of private health care, the effects of the programme have tended to be negligible. In this sense, our central policy recommendation is to optimize the programme for the poorest households in the country.