This study explored the relationships between parents' reports of their children's play with imaginary playmates at home and (1) observational ratings of children's imagination, positive emotionality, concentration, social behavior and use of language during free play at nursery school, and (2) parents' records of their children's television viewing patterns at home. The activities of 141 three- and four-year-olds were observed and rated eight times over one year by trained observers during 10-minute periods of free play in nursery school. Imaginary playmate questionnaires were completed by 111 of the children's parents. Questions concerned indications of the presence and number of imaginary playmates, the frequency of play with such playmates, and the characteristics of the playmates, including the extent to which they reflected the influence of television characters. According to parents' reports, 55% of the children had imaginary playmates at home. Multiple regression analyses indicated that scores reflecting relative occurrence of imaginary playmates predicted the imaginative play of children in school, their positive affect and concentration during play, and their social interaction and cooperativeness. Reports of imaginary playmates tended to be negatively linked to occurrences of overt aggressive behavior (in boys), negatively linked to television-viewing frequency, and positively linked to more extended language use. Additional findings are reported on children's self reports, IQ, socioeconomic status, ethnic background and family structure. (Author/SS)