This study was undertaken to evaluate the usefulness of skin turgor or capillary refilling in estimating the degree of dehydration in infants with diarrhea. After initial standardization of the technique, capillary filling time was found to be more reproducible when measured in the fingernail bed after applying just the amount of pressure necessary to blanch the nail bed. Capillary refilling time in 30 normal infants 2 to 24 months of age was 0.81 +/- 0.31 seconds. Capillary filling time was then measured in 32 infants with diarrhea admitted to the hospital and correlated to the degree of dehydration as estimated from the difference in weight from the time of hospital admission to the weight after rehydration. A turgor time of 1.5 seconds or less was found to be indicative of a less than 50-mL/kg deficit or of a normal infant; 1.5 to 3.0 seconds suggests a deficit between 50 and 100 mL/kg, and more than 3 seconds suggests a deficit of more than 100 mL/kg.