The effects of welding fumes on lung inflammation and injury were examined. Male CD/VAF-rats were intratracheally instilled with a welding fume dose of 1.0 milligram per 100 grams of body weight. Welding fume particles were generated during stainless steel electrode spray welding (SS/SPRAY), mild steel electrode spray welding (MS/SPRAY), and mild steel electrode pulse welding. Silica (68855549) and iron-oxide (1309371) were used as positive and negative controls, respectively. Another control group received saline (7647145) only. Bronchoalveolar lavage fluid (BALF) was obtained from 1 to 35 days following instillation. Lungs were examined 14 and 35 days following instillation. Both histological and magnetometric evaluations were used to determine pulmonary clearance. Compared to the saline controls, the silica and SS/SPRAY groups exhibited elevated neutrophil, macrophage, and lymphocyte counts up to 35 days after instillation. On days seven through 35, the SS/SPRAY and silica groups had significantly increased albumin, lysosomal enzyme, and lactate-dehydrogenase levels in the BALF, compared to the other groups. In the SS/SPRAY and silica groups, significant elevations in tumor necrosis factor alpha and interleukin/1beta levels in the BALF were noted on the first day following instillation. In all treatment groups, the exposure particles tended to accumulate in phagocytic vacuoles within lung macrophages. In mice exposed to SS/SPRAY and silica, mild pneumonitis was found. For the SS/SPRAY and MS/SPRAY fumes, the particle burden in the lung decreased with time. After 35 days, 26% and 56% of the MS/SPRAY and SS/SPRAY particles, respectively, were still present in the lung. Half lives of 47 and 18 days were calculated for the SS/SPRAY and MS/SPRAY particles, respectively. The authors conclude that different types of welding fumes induce different lung responses. The SS/SPRAY fume is more pneumotoxic than the MS fumes.