Oral hygiene, dental caries and periodontal diseases surveyed in 1743 children aged 12-15. Of these 879 of Black origin resided in Haiti (West Indies) and 864 of White origin in Hamburg (West Germany). Oral hygiene was assessed using the Greene & Vermillion's OHI-S, periodontal status using Ramfjord's PDI and Mühlemann's SBI and the caries rate using the DMFT and DMFS indices. Boys of all age groups showed significantly poorer oral hygiene than girls. In the Hamburg children the mean OHI-S was 1.28, in Haitians 1.14. Periodontal diseases showed equal prevalence in Haiti and Hamburg when expressed in PDI, namely 0.59, while SBI was slightly higher in the Haitians, namely 2.58 against 2.21 in the Hamburg Children. Hamburg girls showed lower PDI and SBI scores than all boys and Haitian girls. Same degrees of OHI-S caused more severe periodontal diseases among Haitian than among German children. In general, scores of OHI-S, PDI and SBI increased with age except in Haitian girls, who showed a decrease. The DMFT and DMFS of the Haitian children averaged 3.65 and 4.80 respectively, and those of the Hamburg children 8.35 and 21.09.