Objectives: To assess the feasibility of integrating early psychosocial stimulation into primary care for undernourished children and to determine the effect on children’s development and mothers’ knowledge and practices of childrearing.

Design: Cluster randomised controlled trial.

Setting:  18 clinics in three Jamaican parishes.

Participants:  139 undernourished children aged 9 to 30 months and their mothers enrolled in intervention or control clinics.

Interventions: Weekly home visits by community health aides for one year in addition to usual duties. Parenting issues were discussed with the mothers and play activities were demonstrated with the children using homemade materials.

Main outcome measures:  Children’s scores on the Griffiths mental development scales and mothers’ knowledge and practices of childrearing measured by questionnaires.

Results:  Children from the intervention group showed significant improvements in development: developmental quotient, 7.8 points (95% confidence interval 4.5 to 11.1); hearing and speech, 10.7 (5.9 to 15.4 points); hand and eye coordination, 6.8 (3.4 to 10.1 points); and performance subscale, 11.0 (5.6 to 16.4 points). No improvements were shown on the locomotor subscale. The mothers from the intervention group showed improved knowledge and practices of childrearing. Change in children’s body mass index and height independently affected change in development.

Conclusion:  Integrating parenting skills and early psychosocial stimulation for undernourished children into primary care was feasible and effective in improving the children’s development and mothers’ knowledge and practices of childrearing.