The quinoline dye 2-(2'-quinolyl)-1,3-indandione or Solvent Yellow 33 (SY) and the anthraquinone dye 1,4-di-p-toluidinoanthraquinone or Solvent Green 3 (SG) are used in many manufactured products including military smoke grenades. During manufacturing, SY or a combination of both SY and SG can be released into the air, exposing factory workers by inhalation to these dye compounds. The potential inhalation toxicity of these compounds was tested by exposing F344/N rats to different concentrations of SY or SY/SG dye mixture (30:70 w/w) for 6 hr/day, 5 days/week for 4 or 13 weeks. In the 4-week studies, rats were exposed to SY aerosols at average concentrations of 10 +/- 5, 51 +/- 10, or 230 +/- 30 mg/m3 (means +/- SD) or SY/SG aerosols at average concentrations of 11 +/- 5, 49 +/- 11, or 210 +/- 50 mg/m3 (means +/- SD). Rats exposed to the highest concentration of SY or SY/SG had body weights that were approximately 8% or 7% less, respectively, than their controls after exposure. Rats exposed to the highest concentration of SY/SG for 4 weeks also had reduced pulmonary gas exchange efficiency, airflow obstruction, mild pulmonary inflammation, slight Type II pulmonary epithelial cell hyperplasia, and proliferation of vacuolated alveolar macrophages. In the 13-week studies, rats were exposed to SY aerosols at average concentrations of 1.0 +/- 0.2, 10.8 +/- 1.8, or 100 +/- 17 mg/m3 (means +/- SD) or SY/SG aerosols at average concentrations of 1.1 +/- 0.5, 10.2 +/- 3.1, or 101 +/- 23 mg/m3 (means +/- SD). Animals exposed to the highest concentration of SY or SY/SG for 13 weeks had body weights that were approximately 5 or 9% less, respectively, than their controls after exposure and had accumulation of vacuolated alveolar macrophages in lungs. Rats exposed to the highest concentration of SY/SG dye mixture for 13 weeks also had indications of mild pulmonary inflammation and slight Type II pulmonary epithelial cell hyperplasia. Very little SY was found in lungs after any exposures, indicating its clearance from lungs was at a rapid rate. However, significant amounts of the SG component of the SY/SG mixture were detected in lungs after each exposure. Lung clearance half-times of SG from the 13-week exposure were estimated to be approximately 280 days. In summary, neither test material appeared to be highly toxic following inhalation. However, the slightly higher toxicity observed for SY/SG over SY alone is probably related to the longer lung retention of the SG component of the dye mixture.