The diagnostic value of children's play was investigated. The question explored was "Can maladjusted children be discriminated from adjusted children through observation of their play therapy behavior?" The play of 15 maladjusted and 15 adjusted children 5 to 10 years of age was compared during an initial 36-minute play therapy session. Three scales of the Play Therapy Observational Instrument (PTOI)—emotional discomfort, social inadequacy, and use of fantasy-- were used to rate the children's play. The children in the maladjusted group were referred by their parents for counseling and their teachers reported the children had exhibited one or more problem behaviors indicative of emotional disturbance. The children in the adjusted group were recommended by their teachers as exhibiting none of the problem behaviors and their parents did not believe their children needed counseling. Discriminant function equations predicted correct group membership for 23 of the 30 children during the second 12-minute time segment and for the entire play session. The analysis showed the play behaviors on the emotional discomfort scale of the PTOI items discriminated maladjusted and adjusted children. During the second and third 12-minute time segments and when all three time segments were combined, maladjusted children's play expressed significantly more dysphoric feelings, conflictual themes, play disruptions, and negative self-disclosing statements than were expressed by the adjusted children (p < .01, .03, .01, respectively). There were no significant differences between the two groups on play behaviors measured by the social inadequacy play and use of fantasy play scales of the PTOI. Positive correlations were found between the children's age and social inadequacy play behaviors and between the social status of the parents' occupations and social inadequacy play behaviors. The results also suggested a negative correlation between the social status of parents' occupations and the use of fantasy play scores. A negative correlation was present between the use of fantasy and the social inadequacy play scores.