Deformity of the calcaneus was observed in three patients who developed osteomyelitis after neonatal heel puncture for newborn blood studies. Septic involvement of the calcaneal apophysis may produce an abnormal and early closure of this growth plate. Progressive deformity of the calcaneus, despite appropriate treatment, develops into an asymptomatic flatfoot. A strictly aseptic technique is mandatory for neonatal puncture of the heel to avoid this unusual complication. An infectious cause of flatfoot is proposed in this report.