In order to promote better mental development in three-year-old children from poor Jamaican families, a home-visiting project was carried out with the aim of helping mothers to interact with and stimulate their children. Homes were visited once a week, and the use of toys and books was demonstrated to the mothers. The play equipment was then left with the family and exchanged at the following visit. After a maximum of 29 visits, the children had made significant gains (average 13 IQ points) compared with children in a previously matched control group. The mothers' knowledge of child-rearing had also improved. Similar intervention programmes may be useful on a larger scale, and need not be expensive if full use is made of the mothers' help.