The role of family health-seeking behaviour in under-five-year child mortality was explored through the combined approach of examining health-seeking behaviour regarding treatment generally, and in specific in relation to illness before death. A population-based case control study was carried out during the period 1993–1994 using 222 deaths from diarrhoea and acute respiratory illness (ARI) in children under five years of age in six slums of Karachi as cases, and 419 controls matched on age, disease (diarrhoea and ARI) and slum. Factors significantly associated (p<0·05) with child mortality in the multivariate analysis were: mothers changing healers quickly, using a traditional healer or an unqualified doctor and mothers to whom doctors did not explain the treatment, even when maternal education was controlled for. Seeking effective medical services is highly influential on whether the child survives or succumbs to ARI or diarrhoea. As mothers are the first providers of care, an attempt should be made to try and improve their skills through health education so that they can use simple and effective treatments for minor illnesses. They should also be taught to recognize potentially life-threatening conditions, to seek care early and to persist with treatment.