1. Olfactory receptor cells were isolated from the adult tiger salamander Ambystoma tigrinum and the current in response to odorant stimuli was measured with the whole-cell voltage-clamp technique while odorants at known concentrations were rapidly applied for controlled exposure times. 2. Three odorants, cineole, isoamyl acetate and acetophenone, were first applied at 5 x 10(-4) M. Out of forty-nine cells tested, 53% responded to one odorant only, 22% to two odorants and 25% to all three odorants. 3. The amplitude of the current in response to a given odorant concentration was found to be dependent on the duration of the odorant stimulus and reached a saturating peak value at 1.2 s of stimulus duration. 4. The current measured at the peak of the response for odorant steps of 1.2 s as a function of odorant concentration was well described by the Hill equation for the three odorants with Hill coefficients higher than 1 and K1/2 (odorant concentration needed to activate half the maximal current) ranging from 3 x 10(-6) to 9 x 10(-5) M. 5. It is concluded that olfactory receptor cells are broadly tuned and have a low apparent affinity for odorants, integrate stimulus information over time, and have a narrow dynamic range.