Abstract. Objectives: To determine whether temperatures inside drug boxes used in the out-of-hospital setting are within the U.S. Pharmacopeia recommendations for ''controlled room temperature,'' which is defined as a temperature maintained between 15ЊC and 30ЊC with a mean kinetic temperature less than 25ЊC, and to determine whether timetemperature indicator labels can reliably monitor mean kinetic temperatures. Methods: Two methods were used to monitor temperatures: miniature electronic temperature recorders and color-changing time-temperature indicator labels. These were placed in drug storage boxes of advanced life support units over three summer months and two winter months. Results: In summer, the electronic recorders logged temperatures exceeding 30ЊC in all drug storage boxes, ranging from 3% to 29% of the total time. The mean kinetic temperatures by location for the whole period ranged from 21ЊC to 30ЊC. In the winter, the electronic recorders logged temperatures exceeding 30ЊC at one location 2% of the total time. There were significant temperature excursions below 15ЊC at all locations, ranging from 16% to 90% of the total time. At one location, there were temperature readings below 0ЊC for 9% of the total time. The mean kinetic temperatures obtained from the electronic recorders and the indicator labels differed by less than 1ЊC. Conclusions: This study demonstrates that outof-hospital medications are subject to temperatures both above and below recommended storage temperatures. Time-temperature indicator labels can reliably monitor exposure to elevated temperatures. Key words: EMS; degradation; temperature; drug stability. ACADEMIC EMERGENCY MEDICINE 1999; 6: 1098-1103 M EDICATIONS stored in out-of-hospital vehicles may be subject to extreme temperatures that are out of the safe storage temperature range recommended by the manufacturer. The U.S. Pharmacopeia (USP), 1 which is a quasipublic organization that sets standards for the use of medicines, specifies that manufacturers must indicate on the label of medications the temperature range at which they are to be stored in order to maintain efficacy. The USP 1 also stipulates that ''adequate stability data acquired by the manufacturer should be available to support the expiration date and storage conditions specified.'' ''Further, many drug manufacturers will warrant and guarantee their products' quality, potency and characteristics only if their drugs are stored at recommended storage temperatures. '' 2 In addition, statutes in many states govern the storage of medications on out-of-hospital vehicles. In New Jersey, for example, ''Each vehicle and cabinet or other storage place for medications shall be sufficiently climate controlled so that the medications and solutions are kept within the temperature range recommended by the manufacturer. '' 3 In 1995, for 37 of the 48 medications approved to be carried on New Jersey out-of-hospital advanced life support (ALS) vehicles, the manufacturing label specifies the temperature range requirement...