Ewing's sarcoma in the infant and young child is rare, highly malignant, and can be difficult to identify. An erroneous diagnosis of osteomyelitis may be considered first because the presentation may be similar to that of Ewing's sarcoma, and routine laboratory evaluation may not distinguish between these entities. Two such cases are presented, one involving the tibia in a 16-month-old child and another a finger phalanx in a 7-month-old child. In both cases the correct diagnosis of Ewing's sarcoma was delayed because of initial misdiagnosis of osteomyelitis. This diagnostic dilemma is summarized, and the literature reviewed. Special attention is given to recent advances in histochemistry and cytogenetics that assist in tumor identification. The conclusion highlights areas of remaining controversies for which additional study may facilitate distinction between osteomyelitis and Ewing's sarcoma.