Mating behavior was compared among three populations of Anthocoris antevolens White (Heteroptera: Anthocoridae). Two of the three populations are sympatric in the Yakima Valley, Washington, and are known to differ in length of the setae on the hemelytra and in characteristics of the male’s genitalia. The third population occurred 120 km west of the Yakima populations. All possible inter- and intrapopulation crosses were studied. Males attempted to mate females in all crosses and were as rapid in initiating mating attempts in interpopulation crosses as in intrapopulation crosses. Mating success, defined to be insemination of the female, varied between 64 and 92% in intrapopulation crosses, but only between 0 and 21% in interpopulation crosses. The crosses between the two sympatric populations never resulted in insemination. Females in all crosses resisted mating attempts by males. Resistance behavior included hunching of the abdomen to prevent insertion of the clasper by the male, use of a hind leg to block male attempts to insert the clasper, and attempts to dislodge the male. For two of the populations, female resistance increased when paired with a male from a different population than when paired with a male from her population; females from the third population showed similar levels of resistance in interpopulation and intrapopulation crosses. Our results support the idea that A. antevolens is actually composed of an unknown number of reproductively isolated cryptic species.