The categorization of voiced and voiceless syllable-initial stops is dependent primarily on voice onset time (VOT), but has been proposed to be sensitive to first formant (F1) transitions and place of articulation. The present study tested the effect of both F1 transition and place cues on the categorization of voiced and voiceless stops in a /(schwa)Ca/ context (second syllable stress). Three different stop properties were independently manipulated: VOT, F1 onset frequency, and place of articulation. VOT was varied along a 0 to 65-ms continuum. Four different F1 onset frequencies for the /Ca/ transition were used. Place (labial, alveolar, and velar) was cued by both the release burst and higher formant transitions into and out of the stop. The effects of F1 transition and place on voicing judgments were measured by shifts in the VOT identification boundary. The effect of F1 on voicing judgments would be interpreted as resulting from a general mechanism of audition nonspecific to speech, following Kluender [J. Acoust. Soc. Am. 90, 83--96 (1991)] who found that categorization of burstless CV stimuli from a VOT continuum is sensitive to F1 onset frequency, but not place. In contrast, an effect of place on voicing judgments would be interpreted as the result of a phonological category determining phonetic criteria, in this case place determining VOT thresholds.