A whole population inner-city survey identified 23 stunted, otherwise healthy, children with persistently poor growth from infancy to 4 years. Their cognitive development was significantly retarded relative to a matched comparison group. Unstructured home observations were used to create transcripts of verbal and nonverbal mother-child interactions. In both groups child behavioural adjustment was linked to maternal negativity, and cognitive performance was correlated with quality of stimulation. The developmental delay associated with chronic failure to thrive appeared more likely to arise from other influences, perhaps a previous biological insult, than to contemporaneous parenting practices.