- BACKGROUND AND PURPOSE: The Gross Motor Function Measure (GMFM) is a criterion-referenced observational measure for assessing change in gross motor function for children with cerebral palsy (CP). The purposes of this report are to present data on the effects of training pediatric developmental therapists to administer and score the GMFM and to discuss some practical and methodological issues associated with training. SUBJECTS AND METHODS: A weighted kappa estimate pretraining and posttraining workshop was used to determine participants' agreement of scoring a videotaped GMFM assessment against experts' scoring of the same videotaped assessment. Several children with CP, representing a spectrum of ages, severities, and levels of function, were shown on the videotape. RESULTS: There was a significant improvement in agreement from a mean kappa of .58 to .82 (t = 15.38, df = 75, P < .001) for the first group and from .81 to .92 (t = 10.91, df = 72, P < .001) for the second group following training. CONCLUSION AND DISCUSSION: Although there are a number of advantages to using videotapes to train test users and to assess scoring reliability, this method does not evaluate participants' ability to administer the measure. Further work is needed to determine whether reliability is maintained in a clinical situation in which it is necessary to both administer and score the GMFM.