The reliability of the Functional Independence Measure for Children (WeeFIM) was examined in 37 non-disabled children and 30 children with disabilities, from 12 to 76 months of age. The WeeFIM is derived from the Functional Independence Measure (FIM) and includes 18 items involving six functional subscales. Stability was assessed by administering the WeeFIM instrument to each child's caregiver on two occasions separated by 7 to 14 days. Intraclass correlation co-efficients (ICCs) for individual items ranged from 0.90 to 0.99. The ICC for the six WeeFIM subscales ranged from 0.94 for social cognition to 0.99 for transfers and locomotion. The ICC value for total WeeFIM test-retest reliability was 0.98 for children with disabilities and 0.99 for children without disabilities. Equivalence reliability was examined by comparing ratings obtained when using personal assessment with ratings collected during a telephone interview. No statistically significant differences were found for individual items, subscale scores or total WeeFIM values.