Repellency of moving ambient air to American, Periplaneta americana (L.), and smokybrown, Periplaneta fuliginosa (Serville), cockroaches was evaluated with modified Ebeling choice boxes by using air velocities of 0-4.75 m/s. All measured stages (adult female and male, and medium and large nymphs) of both species were significantly repelled by air velocities greater than or equal to 4.0 m/s. Percentage of repellency increased exponentially with air velocity for American, hut increased linearly for smokybrown cockroaches. Male American cockroaches detect moving air with mechanoreceptors located on their antennae and cerci. Differences in response to air velocity may help explain the absence of smokybrown cockroaches from sewerage systems. Moving air may be useful as a noninsecticidal tactic in an integrated pest management system for American and smokybrown cockroaches control.