Effects of brief time out on the biting behavior of a 21- month-old boy enrolled in a day care setting was examined. The Motivation Assessment Scale (MAS; Durand, 1983) was used to determine the function of the child's biting. A parent report survey, the MAS assesses disruptive behavior using a Likert-type scale and discriminates the function of a target behavior into one of four categories: self-stimulation, escape-avoidance, social approval, and access to preferred reinforcers. Results of the MAS indicated that biting served the function of gaining access to adult attention; in this child's case, verbal attention from both mother and day care provider. Treatment consisted of time out used contingently with instances of or attempts at biting others. When the treatment program was initiated in the day care home, the incidence of biting decreased to an average of .6 for the first week, .4 for the second week, and to 0 by week seven. When treatment was implemented at home, the decline in biting was initially less dramatic, due to the mother's incomplete implementation of the time out intervention. A correction to the same procedure used in the day care home led to an immediate reduction in biting at home to .1 per week at week six and the disappearance of biting 2 weeks later. In both settings, biting was absent at 9- and 10-week follow-ups. (RH)