A triple cage olfactometer provided with insect traps was used for evaluating behavioral responses of Stomoxys calcitrans (L.) females to human skin and breath, CO₂, and L-lactic acid analogs. After demonstrating there were no significant differences caused by cage location or time of day, 3 sets of 3 olfactometer tests were performed in a day, every 2 h beginning at 0900 hours. When a human hand was used as attractant, the attraction (expressed as percentage of trapped flies) increased as a function of the time; an inverted U-shaped relationship between attractancy and air speed was observed; and variation in fly density in the range 25–75 per cage did not affect the attraction response. When human breath was used as attractant the attraction increased linearly as a function of time and it was exhalation frequency dependent; when air flow was absent the highest response was observed; and 24- to 38-h-old flies were more attracted than younger and older. When CO₂ was tested, activation and orientation and probing behavior were concentration dependent with flows ranging between 0.0001 and 0.038 liter s⁻¹, but attraction was not. No attraction was observed with 10, 100, or 1,000 μg of compounds related to L-lactic acid and several synthetic human odors and related compounds, although orientation was often observed.