Children aged 9-24 mo were recruited by a survey of poor areas of Kingston, Jamaica. Stunted children were randomly assigned to supplementation or not. Weekly morbidity histories were taken for 2 y. Separate multiple regressions on each symptom for weight or length gain in 2-mo intervals showed significant reductions in weight gain with coughing, apathy, anorexia, diarrhea, and fever, ranging from -2.1 to -16.8 g/d ill. Apathy and diarrhea reduced gains in length (-0.26 and -0.20 mm/d ill). Significant reductions in linear growth with lower respiratory-tract infections (-0.16 mm/d ill) occurred only in nonsupplemented children. Growth over 4-mo intervals was reduced if diarrhea occurred in the first 2 mo of the interval but there were no long-term effects of apathy, fever, or anorexia. Some of the effects of morbidity on growth were therefore transient and morbidity is unlikely to be a major cause of growth retardation in this population.