PIP: To study the effects of narcotics on plasma testosterone a single dose of methadone was given to 8 male volunteers. There were no significant changes in plasma testosterone, prolactin, FSH or LH level; plasma methadone levels rose. Although patients' plasma containing higher levels of methadone tended to have lower testosterone levels, no simple relationship was found. Daily methadone doses in stable tolerant individuals did not produce adverse effects on plasma pituitary or testosterone hormone levels.