Abstract. [Purpose] We used the Japanese version of the Aberrant Behavior Checklist (ABC-J) to investigate whether or not physical therapists (PT) and occupational therapists (OT) assess problematic behaviors of handicapped children differently.[Subjects] The subjects were 11 mentally-retarded children undergoing physical therapy at T Hospital. The examiners were classified into two groups: PT and OT. Wilcoxon's signed rank sum test was conducted on the two groups' ABC-J scores for, irritability, lethargy, stereotypy, hyperactivity and inappropriate speech scores. [Results] No significant differences between the two groups were observed for most problematic behavior types, although the effect sizes were small. Physical therapists, however, assessed the lethargy of the subject children as more problematic than occupational therapists did. [Conclusion] The results that some bias may occur depending on examiner occupation, although the ABC-J allows anyone to be an examiner as long as he/she knows the subject child well.