A review of renal histology from 44 neonatal and pediatric autopsies, all with documented intensive hospital courses, identified 8 cases showing varying degrees of microscopic calcium deposition. Histochemical and x-ray spectroscopic microanalysis showed that all eight cases contained intratubular deposits of calcium oxalate, and two cases contained both oxalate and phosphate microliths. The spatial arrangement of the deposits appeared to vary with the density of deposition. A control group of 68 non-intensively treated cases (stillbirths and sudden infant death syndrome cases) showed rare calcium phosphate microliths but none had oxalate crystals. Infantile nephrocalcinosis is little understood and is poorly documented in the current literature. This study may contribute to the understanding of this entity and may be useful in guiding stratagems to prevent its occurrence.