Trachoma remains the major infectious cause of blindness in many developing areas, especially where hygiene is poor. The practices and behaviors associated with an increased risk of trachoma were studied in central Tanzania, where a stratified random cluster sample of 8409 people was examined. Data were collected on family and individual characteristics and behaviors and on trachoma status. Overall, 60% of the children aged 1 to 7 years had active inflammatory trachoma, and 10% of those aged 60 years or older had trichiasis. Regression analysis showed that active inflammatory trachoma in children was associated with the characteristics of the more traditional families and several measures of poor personal hygiene. Two important risk factors for severe inflammatory trachoma were poor facial cleanliness in children (odds ratio of 1.7 [1.17, 2.50]) and household fly density (odds ratio of 1.63 [1.17, 2.29]). Both factors are potentially amenable to intervention. These data suggest that an intervention strategy aimed at these hygiene measures would provide an effective method of controlling trachoma in this region, and a similar approach may be useful in other areas.