This study was conducted to investigate the swarming and mating behaviors of wild and irradiated males An. Arabiensis. Male mosquitoes were irradiated as pupae and transported as adults to the field. The wild ones were collected as larvae in the field and reared to adult. Both irradiated and wild-reared insects were dusted with fluorescent powder (PF). Search for swarming insects started before the sunset. When allocated, males and coupling pairs were sampled from swarms. Captured females were dissected under microscope for parity and insemination rates. Wings of males from swarms and in copula were mounted and measured using stereoscope. Locations of swarms were marked using a GPS. The landmarks in swarm locations were characterized. The numbers of males and pairs at 3 locations were counted every 2 min intervals in the swarm. Irradiated males were released before the sunset and search of marked insects in swarms was done at evenings. In addition, wild males and virgin females were released in the semi-field enclosure. Direct observations on mating and swarming behaviors were made in the system.