Peroxynitrite prepared from superoxide and nitric oxide in liquid ammonia does not contain detectable levels of nitrite. However, the dissolution of nitrite salts can lead to variable levels of peroxynitrite depending on the conditions used to disolve the salt. Low levels of nitrite result when frozen peroxynitrite solutions are first brought to +1 degreesC and then to room temperature. These undergo only 2-3% decomposition after 1 h, in contrast with the findings of a recent report (Lymar, S. V.; Khairutdinov, R. F.; Hurst, J.K. Inorg. Chem. 2003, 42, 5259-5266), where high levels of nitrite (similar to20%) result from rapid thawing of these solutions to room temperature. Warming the frozen peroxynitrite solution directly to room temperature in 30 min leads to a nitrite level of 28%.