A randomised controlled trial was conducted to evaluate the effect of a motor developmental program in improving motor performance in Thai infants born preterm. Eighty-four preterm born infants were randomly assigned to either a control or intervention group. Additionally, 27 low-risk preterm infants were included forming a comparative group for this study. From term equivalent age to four months adjusted age, all infants had their motor performance assessed monthly with the Test of Infant Motor Performance by one of the physiotherapist research assistants blind to group assignment and infants' adjusted age. In addition, the intervention infants received a developmental program at each monthly visit. Motor performance for each group plotted against age revealed linear trends of progression. The intervention group showed the greatest improvement. Two-way repeated measures ANOVA revealed significant differences across age and among groups. Scheffé comparisons indicated that the mean differences between each pair of the three groups were significant and supported the finding of greater improvement of the intervention infants over the control group. Thus the results suggest that the intervention program is likely to have beneficial effects when offered to a similar population of preterm born infants.