The toxicity of T-2-toxin (21259201) was investigated in Long-Evans- hooded-rat alveolar macrophages (AM) in-vitro. The viability of control cultures was 96 percent, whereas cultures containing T-2- toxin at concentrations of 0.001 and 0.01 micromolar (microM) showed a viability of 93.8 and 89.9 percent, respectively. In cultures incubated with 1 and 10microM T-2-toxin, the viability was reduced to 51.9 and 47.7 percent. Cultures containing T-2-toxin concentrations of 0.001, 0.01, 1, and 10microM had cell number values of 79.8, 69.0, 30.3, and 29.4 percent, respectively. Viability determinations after exposure of AM to submicromole concentrations of T-2-toxin for 20 hours demonstrated that the toxin was cytotoxic at determinable concentrations and that the effect of T-2-toxin on AM viability, cell number, and viability index was dose dependent. T-2-toxin treatment also caused a dose dependent leakage of chromium from the cells. Surface morphologic alterations were noted on scanning electron micrographs which reflect varying degrees of cell damage. Most of the cells lost their surface membrane features and developed bleblike structures and many lysed cells were also evident. The authors conclude that submicromolar concentrations of T-2-toxin are cytotoxic for rat AM. Whether or not this indicates that T-2-toxin poses an environmental hazard for agricultural workers exposed to mycotoxin contaminated grain dust must be examined.