A total of 28 male patients objectively diagnosed with obstructive sleep apnea syndrome (OSAS) participated in specific drug trials involving naloxone (an opioid antagonist), theophylline and bromocriptine mesylate (a dopamine agonist). All subjects were between 15 and 40% overweight. The group median apnea-hypopnea (A + H) index was 58. None of the drugs had any significant beneficial effects on the number and duration of upper airway apneas and hypopneas or directly related oxygen desaturation. Theophylline increased the diaphragmatic activity during REM sleep-related mixed apnea but had no impact on upper airway apnea in the studied population.