Musical improvisation behavior of 4-, 6-, and 8-year-old children who played Orff xylophones during ten 15-minute sessions is described in this paper. Each session involved three improvisatory phases. Phase I consisted of free exploration; Phase II consisted of short verbally stimulated musical tasks (two imitation and six improvisational tasks); and Phase III consisted of a folk song played by the investigator followed by improvisations by subjects while the investigator played a 24-measure bordun accompaniment. Each session was recorded, and improvisations from Phase III were isolated for analysis. Children's initial responses, their sequences of behavior, and the musical structure of their improvisations were analyzed. Among the results, it was found that the characteristics of children's improvisation change in relationship to the child's chronological age. Young children are able to improvise patterns which are related to melodic and rhythmic stimuli. Four- to eight-year-old children are able to form musical images to verbal stimuli. The 4-year-old child improvises complex rhythm patterns. Six-year-old and eight-year-old children maintain their interest in exploring the sound possibilities of a single instrument longer than four-year-old children. Between the ages of 6 and 8 children may improvise large formal structures. (Author/RH)