One hundred thirty-nine children younger than 4 years were identified retrospectively from the period of 1993 through 1997 to have an isolated fracture of the shaft of one or both femurs. Abuse was classified as group A (definite, likely, or questionable abuse) or group B (unknown cause, questionable accident, likely accident, or definite accident). The average age of the children was 2.3 +/- 1.1 years. Thirteen children, 9% of the total group, average age of 1.1 +/- 1.0 years, were likely to have been abused (group A). A total of 126 children, 91% of the total, average age 2.3 +/- 1.0 years, sustained their fracture most likely as a result of an accident (group B). Whether a child had not yet achieved walking age (toddler) was the strongest predictor of likely abuse. Ten (42%) of 24 of nonwalking children were in group A, whereas only three (2.6%) of 115 of walking children were in group A (p < 0.001). Child Protective Services may have been unnecessary in 42-63% of cases. Unless other evidence of abuse such as an inconsistent story, bruises, or other fractures are present, abuse is very unlikely to be involved in the walking-age child, analogous to the toddler fracture of the tibia.