DNA damage of the bone marrow cells in mice exposed to sulfur mustard (SM). Male KM mice were exposed to saline, propylene glycol (PG) and 20 mg/kg SM by subcutaneous injection. Six animals from each group were sacrificed after SM exposure at 4 h, 24 h, 72 h and 168 h, and a bone marrow cell suspension was prepared and assayed by single cell gel electrophoresis technique (SCGE) as described in the Materials and Methods(A). The TL (B1) and the percentage of comets (B2) were evaluated to assess SM-induced DNA damage. Data are presented as the mean ± SD, n = 6 for each group (B1-B2). *Significant difference between the PG treatment and SM exposure groups (**P < 0.01, ***P < 0.001).