The effects of maternal marijuana use on the newborn cry were studied in Jamaica, where it was possible to rule out confounding factors such as the use of other substances and demographic variables that have clouded previous studies and where higher dosages may make the effects more visible. The acoustic characteristics of the cries of 20 infants of marijuana users and 20 controls were analyzed. The cries of the infants of marijuana users were shorter, had a higher percentage of dysphonation, a higher and more variable fundamental frequency, and a lower first formant than controls. There was also a dose response relation between the first formant and marijuana use. We suggest that heavy marijuana use affects the neurophysiological integrity of the infant.