BCNU is increasingly used in low ethanol (ETOH) concentrations, 5% dextrose-water (D5W), or normal saline (NS) solutions, especially for intra-arterial and prolonged (e.g., 3 day) intravenous (IV) infusions. Little work, however, has been done to evaluate BCNU decomposition rates in concentrations, diluents, and temperatures similar to those employed clinically. This study examined B CNU solutions in ETOH, NS, and D5W to evaluate, conclusively, initial recovery and decomposition rates in these three diluents. Initial BCNU recovery rates were: 95.6 + 0.3% (100% D5W), 89.6 _+ 0.5% (15% ETOH), and 85.2 _+ 0.5% (NS) (P < 0.001). Study of all solutions revealed no measurable BCNU decomposition over 24 hrs (0 Β° C) and no significant difference in decomposition rates between any of the diluents (19.5 Β° C). At 37 Β° C, the solutions showed different half-lives: 14.3 + 0.19 hrs (15% ETOH), 10.6 _+ 0.02 hrs (10% ETOH), 8.2 _+ 0.21 hrs (5% ETOH), 7.3 + 0.06 hrs (NS), and 6.8 + 0.07 hrs (D5W) (P < 0.001). Decomposition rates between all three temperatures (19.5 Β° C, 37 Β° C, and 50 Β° C) were significantly different (P < 0.01) for each diluent. Dissolving BCNU powder into either D5W or NS required only 5 rain when hand-shaken at body temperature. This study of initial recovery and decomposition rates suggests that, although BCNU decomposition rates were significantly increased at body temperature (37 Β° C), it was quite low and essentially unaffected by different diluents at room temperature (i.e., 19.5 Β° C). D5W as a diluent for BCNU appeared to provide significantly higher recovery than NS or 15% ETOH with no significant difference in half-life at room temperature and thus appeared a practical alternative diluent to ETOH for infusions.