In April 1992, the American Academy of Pediatrics recommended back or side sleeping for healthy newborns to reduce the risk of sudden infant death syndrome. Subsequently, the US Public Health Service organized a health care coalition to promote a "Back to Sleep Campaign" to advocate back or side sleeping for infants. Since 1992, our craniofacial anomalies center has witnessed a marked increase in the incidence of infants with defomational changes of the cranium and face. The purpose of this project was to study the etiologies of deformational plagiocephaly and possible correlation with infant head position. We reviewed 52 consecutive patients presenting with deformational plagiocephaly from January 1992 to December 1994. A diagnosis of deformational plagiocephaly was determined by (1) history (date when head shape change was first noted), (2) clinical examination (occipital flattening, contralateral forehead flattening, lowering of the eyebrow, and ear shearing), and (3) skull radiographs (patent cranial sutures). All infants had medical photography to document baseline craniofacial morphology and any follow-up changes after nonsurgical therapy. Cranial asymmetry was first noted after birth at a mean time of 3.6 months. All infants were initially positioned on their back/side. In 52 patients, 61% had right-sided flattening of the occiput (vs 39% left-sided). All infants had flattening of the occiput, contralateral brow lowering or inferior displacement of the brow, contralateral forehead flattening, and posterioinferior displacement of the ear. All skull radiographs demonstrated patent sutures. Follow-up of patients ranged from 3 to 22 months with a mean of 10.5 months. Follow-up clinical examination and photography demonstrated significant improvement of cranial form in all patients with recommended frequent head turning (73%), helmet molding (23%), and surgery (4%). Our unit has seen an increase in the number of infants with deformational plagiocephaly over the last three years. All of the affected infants in this study had been managed according to the officially recommended protocol of back/side positioning. These findings suggest a possible relationship between this type of infant positioning and the development of a deformational plagiocephaly. However, cranial asymmetry in this group of patients decreased significantly with nonsurgical therapy. We have not recommended cranial vault remodeling surgery for the mild and moderate types of this deformity. However, if there is evidence of increasing asymmetry of deformational plagiocephalic infants during follow-up and evidence of severe variants of these deformities, surgical correction of the cranial vault is recommended.