Single-use diapers and cloth diapers with vinyl pants were compared for their relative abilities to contain stool within the diaper. Artificial feces with carbon black as an additive allowed a quantitative measure of fecal containment by image analysis in 60 infants. This method showed complete containment of feces in the diaper in 50% of the single-use diapers whereas only 10% of the cloth diapers showed complete containment. In infants where the border of the vinyl pants was used as the boundary of containment with the cloth diapers, complete containment occurred only 33% of the time. Fluorescein dye ratings for containment/leakage in 69 infants showed that 83% of single-use diapers and 30% of the cloth diapers were rated as having no or minor leakage of feces. Cultures were taken of laundered vinyl pants that had previously been used over cloth diapers to determine microbial contamination. Thirty-nine percent of the pants contained Gram-negative, lactose-fermenting bacilli indicating fecal contamination. This study comparing single-use and cloth diapers for containment of artificial feces by use of image analysis and fluorescein dye ratings showed better containment by single-use diapers. The study also raises the question of possible spread of feces-borne pathogens by the vinyl pants used over cloth diapers, particularly in a day-care center.