A computer-controlled olfactometer with several innovations leading to closer control over the stimulus parameters and minimization of nonolfactory cues is presented. A microcomputer is used to control the stimulus duration and interstimulus interval. Electronic mass flow controllers are employed to maintain close control over the flow in the pure air line and the stimulus-bearing line. Both humidity and temperature are closely regulated. Using a nasal catheter, this stimulus delivery system coupled with velopharyngeal closure and oral breathing permits accurate specification of the quantity of stimulus material actually entering a subject's nares. The design is such that the computer programming, patch panel interface, and threaded tubing allow versatility in the type of olfactometric study that can be conducted. This system is amenable for threshold, electrophysiological, and sensory adaptation studies of olfaction.