Two brothers demonstrated a severe variant of trichothiodystrophy. Both had brittle hair, developmental delay with severe failure to thrive, recurrent infections, cataracts, and angioendotheliomas of the liver at autopsy. The elder died at 12 weeks, the younger at 6 months. The younger had the typical appearance of banded hair on polarizing microscopy and a low cystine content measured by ion exchange chromatography. The history, clinical findings, and basic defects of trichothiodystrophy are discussed.