Larynges from 13 victims of sudden infant death syndrome (SIDS) and from ten controls of comparable age were subjected to serial histological transverse section and examined for structural differences that bear on functional performance. The cross-sectional area of mucous glands in the vestibular fold, expressed as a percent of the total cross-sectional area of the fold was 19.52 +/- 8.56 (mean +/- SD in the SIDS specimens), and 12.56 +/- 6.25 in the controls. The difference is statistically significant and suggests that excess mucous laryngeal secretion may be present in at least some cases of the syndrome.