A review of recent studies of early childhood altruism is followed by a report of a study of development of altruism in early childhood at ages 3, 4 and 5 years in terms of children's ability and willingness to help, share, and donate. 178 preschool children were videotaped while interacting in pairs matched by age and sex in an age-appropriate, structured altruism task in which opportunities to help and share arose in the natural flow of events. Results indicate that even the youngest children (age 3) displayed some altruistic acts; both the number of children showing altruism, and their number of altruistic acts, were greater at each succeeding age level. Sharing was the most common altruistic behavior, and it was more frequent than helping and donation behaviors at earlier ages. Possible explanations for the different developmental trajectories of different altruistic acts are discussed, with emphasis on the differing cognitive and empathic demands of the situation. Main contributions of the study include demonstration of (1) different developmental trajectories for different types of altruistic acts; (2) age-related increase in spontaneous altruistic acts toward peers between 3 and 5 years of age; (2) the utility of a naturalistic, structured observational task to study spontaneous altruism towards peers in young children.