Pupae of the blueberry maggot, Rhagoletis mendax Curran (Diptera: Tephritidae), were subjected to -20 degrees C for 2, 4, 7, 10, and 15 d (control = 0 d at 4 degrees C) in fall 2011 and 2012 and were allowed to overwinter for at least 181 d at 4 degrees C. Mean adult emergence in the control was 64% in 2012 and 39% in 2013. No adults emerged in May 2012 from 500 pupae treated for > 2 d at -20 degrees C in fall 2011. Two adults emerged in May 2013 from 100 pupae treated for 2 d at -20 degrees C in fall 2012. No adults emerged in May 2013 from 400 pupae subjected to -20 degrees C for durations of 4, 7, 10, and 15 d. No adults emerged from larvae concealed in berries subjected to -20 degrees C for > 2 d. Exposure of larvae and pupae to cold temperatures (i.e., -20 degrees C) for > 2 d can be a valuable nonpesticidal method for killing R. mendax larvae and pupae associated with reusable containers.