Reduced serum levels of vitamin A affect morbidity and mortality in measles. The authors' newly diagnosed subacute sclerosing panencephalitis (n = 21) and age-matched control groups (n = 20) had mean serum beta-carotene levels of 1.12 +/- 0.56 and 1.50 +/- 0.52 microg/mL, respectively. Serum retinol <20 microg/dL was observed in 6 of 21 subacute sclerosing panencephalitis and 0 of 20 control cases (P < .05). Vitamin A deficiency can accompany subacute sclerosing panencephalitis: its contribution to the pathogenesis or course of the disease warrants further investigations.