Eighty-one prepubertal beef heifers were used to evaluate effects of used controlled internal drug release (CIDR) insert heating methods on concentrations of progesterone after CIDR insert reinsertion. Heifers were stratified by weight and birth date and then assigned to receive a new CIDR insert (New; n = 10) or 1 of 8 used (7 d prior use) CIDR insert treatments: 1) no processing (Used; n = 10), 2) autoclaved (Autoclaved; n = 8), 3) processed in dishwasher (Dishwasher; n = 8), 4) processed in microwave for 30 s (Microwave; n = 10), 5) processed in toaster oven (Oven; n = 9), 6) processed in clothes dryer (Dryer; n = 10), 7) processed in boiling water (Boiled; n = 8), or 8) stored outdoors for 60 d (Outside; n = 8). Used CIDR inserts were processed at 121°C for 30 min for autoclaved and oven treatments, at 121°C for boiled treatment, and for 30 min for dryer and dishwasher treatments. Blood samples were collected on d -10, immediately before CIDR insert insertion (d 0), 3 h after CIDR insert insertion (3 h), daily while CIDR insert was in place (d 1 to 11), and 24 h after CIDR insert removal (d 12) for analysis of concentrations of progesterone. Subjective color scores (1 = bright white to 5 = completely stained yellow/red) were assigned to each CIDR insert after d 11. A treatment × time interaction (P < 0.0001) was present for concentrations of progesterone. Concentrations of progesterone were similar (P > 0.10) for heifers receiving a used CIDR insert compared with heifers receiving CIDR inserts processed in a dishwasher, microwave, oven, dryer, or boiling water (collectively reported as "Processed"). However, heifers receiving autoclaved CIDR inserts had greater (P < 0.05) concentrations of progesterone from h 3 to d 3 but similar (P > 0.10) concentrations of progesterone from d 4 to d 11 compared with heifers receiving used or processed CIDR inserts. From d 1 to 11 heifers receiving outside CIDR inserts had decreased (P < 0.05) concentrations of progesterone compared with all other treatments. Heifers receiving autoclaved CIDR inserts had greater (P < 0.05) concentrations of progesterone compared with all other treatments at 3 h and 1 d, whereas heifers receiving new CIDR inserts had greater (P < 0.05) concentrations of progesterone from d 6 to 11 compared with all other treatments. Outside CIDR inserts were more discolored (P < 0.001) compared with all other treatments. Processing used CIDR inserts with a dishwasher, microwave, oven, clothes dryer, boiling water, or full environmental exposure did not result in a pattern of concentrations of progesterone similar to that of autoclaved or new CIDR inserts.