SummaryTo date questionnaire surveys have been the most commonly used instruments to measure hygiene behaviours related to water and sanitation. More recently, a number of studies have used structured observations to study practices related to diarrhoea. During a trial of a hygiene education intervention to reduce diarrhoea among young children in Bandundu, Zaire, both instruments were used to measure the disposal of child faeces and various hand-washing practices. Three hundred families were observed and follow-up interviews performed with 274 (91%) mothers. At the individual level, agreement between observed and reported behaviour was little better than might be expected by chance. There was evidence of over-reporting of hand-washing before food preparation (44% vs 33%; P ϭ 0.03), hand-washing before eating (76% vs 60%; P Ͻ 0.001) and disposal of the child's faeces in a latrine (75% vs 40%; P Ͻ 0.001). On the other hand, hand-washing before feeding the child was reported less often than it was observed (7% vs 64%; P Ͻ 0.001). Our data are consistent with the hypothesis that, in general, mothers over-report 'desirable' behaviours. At the same time, our data indicate that open questions may lead to underreporting of certain behaviours. The repeatability of observations at both the individual and population levels remains to be established.

The results of this study suggest that hygiene education may be an effective approach to reduce the incidence and duration of diarrhoeal episodes in rural Zaire. Children aged 2 years appear to benefit the most. A Hawthorne effect of the education may contribute to diarrhoeal reductions.

A community-based prospective study of diarrhoeal morbidity of weaning-age children in 18 geographically separate village clusters was conducted as the baseline phase of a controlled trial of a hygiene education intervention to reduce diarrhoeal diseases in rural Zaire. For 12 weeks trained interviewers collected information at weekly home visits about the diarrhoeal morbidity of 2082 children aged 3-35 months. Included in the analyses were 1914 children (92%) with 9 or more complete weeks of data. Mothers' reporting of the existence or otherwise of episodes appeared reliable, and more than 70% of children had at least one episode of diarrhoea during the 12-week study period, the mean number of episodes being 1.9 per child. Reporting of the start and termination of diarrhoeal episodes was, however, irregularly distributed among the 7 days between successive home interviews, with 36% of all episodes reported as starting on interview days, and 29% reported as ending the day before an interview: in each case, only 14% would have been expected. After adjusting for these reporting biases, 61% of the episodes lasted 2-4 days, but a number of very long duration were also reported, and the mean duration of the episodes was 4.8 days. Children, had, on average, 9.2 days of diarrhoea during the study period. Contrasts with previous characterizations of reporting error in diarrhoeal studies are noted.