In a study of 751 mothers whose children had home based growth charts, 62 per cent understood the purpose of the weight marks and could distinguish a good from a bad weight; 49 per cent understood the purpose of the upper line, 47 per cent the lower line, and 45 per cent the space in between. Literate mothers (n = 75) did better than illiterate (P < 0.001). Growth, as measured by change in weight for age, was no different in children whose mothers understood the chart and those who did not. Since explanation of the chart to mothers uses staff time, this area should be the subject of further study.