A multiple baseline design for modifying the gross motor coordination of a 31-month-old boy suspected of suffering from congenital brain damage was conducted at the University of Kansas Infant Study Laboratory. The primary purpose of the study was to establish, by experimental procedures, the desired, but absent, behavior of walking, getting up, and climbing stairs, at the expense of the existing behavior of scooting, pulling up with support, and not climbing stairs. It was hypothesized that, incidental to establishing the three desired behaviors, the behavior of standing without support would replace the subject's need to stand with support. The training sessions for each of he three desired behaviors were based on the gradual modification of undesirable into desirable behavior through selective reinforcement. The three desired behaviors were initially of zero incidence but were ultimately established as part of the child's response repertoire, although not to the complete displacement of the undesirable behaviors. (WD)