Exposure to cold temperatures or CO2 has been used often to immobilize insects and several studies have dealt with the short and long term effects of exposure to cold and CO2 (Edwards & Patton 1965, Edwards 1968, Hooper 1970, Speirs & Zettler 1972, Berger & Zeyen 1987, Nicolas & Sillans 1989). Brief exposure to CO2 was used to anesthetize adult leafminers, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae), for toxicity studies with negligible effects on survival (Parkman & Pienkowski 1989); however, exposure to cold temperatures could have been used. This study was conducted to determine the short-term effects of cold temperatures or CO2 at various exposure times on the survival of adult female L. trifolii. Individuals used were from a L. trifolii colony maintained at Virginia Polytechnic Institute and State University for approximately 280 days (= 14 generations at 25?C). They were maintained on chrysanthemums, Dendranthema morifolium (Ramat) Tzvelev. cv. 'Manatee Iceberg, at 25 + 3?C, 50 + 10% RH, and a photoperiod of 14:10 (L:D). To determine the effects of cold temperatures on adult survival, female L. trifolii ( 0.05) (Table 1). Significantly more females died after the 4 h exposure at -5?C than after exposure periods of less than 1 h (F = 4.77; df = 8,15; P < 0.05) (Table 1). Mortalities of greater than 90% occurred after exposures of 2 h or longer at -10?C which were significantly greater than mortalities at exposure periods of up to and including 1 h (F = 12.16; df = 8,15; P < 0.01) (Table 1). Significantly more adults died when exposed to -10?C than at -5' and 0?C for all exposure periods, while there was no significant difference in mortality for adults exposed to -5' compared to those exposed to 00 for all exposure periods (Table 1). Mean percent mortality + SD for the control group, 2.1 + 4.2%, was significantly less than mortality occurring for all exposure periods at-10?C(F = 24.93; df = 9,18; P < 0.01) and for mortality occurring