Upper airway involvement in the sudden infant death syndrome (SIDS) continues to be a prime consideration. Coexistemce of susceptibility to apnea in response to stimuli and weak compensatory response to hypoxia may provide the situation where certain stimuli are lethal in the rapidly maturing infant of age less than one year. In a recent study, mucous gland concentrations in the larynxes of SIDS victims were found to be 1.55 times greater than in non-SIDS victims. It is suggested that excessive mucous may be a source of lethal stimulus. In this application it is proposed to investigate the use of ultrasonic spectroscopy for the purpose of measuring gland concentration in living infants. The major features of a final instrument and how it would be used to study SIDS with living infants are outlined. The key questions concerning the feasibility of the instrument are to be investigated in this study. Autopsy human specimens and specimens from young animals will be used to evaluate ultrasonic measurement techniques. Based on the results of the study, conclusions will be drawn and recommendations will be made concerning the development of an ultrasonic unit for use with living infants.