Methyl methacrylate (MMA) is a monomer, commonly used in neurosurgery, orthopedic surgery, and in dental clinics. The adverse effects of this monomer are well described in the literature. This study was designed to evaluate the effects of MMA on nasal cavity, lung, and antioxidant status. For this purpose, two experimental groups of rats were exposed to MMA (at 1000 ppm, 6 h/day, 5 days/week for 4 weeks) by inhalation under poor (group A, n = 12) and normal ventilation (group B, n = 11) conditions. A control group (group C, n = 10) received normal air. Degeneration of olfactory epithelium, bronchopneumonia, interstitial pneumonia, hemorrhage, atelectasis, edema, emphysema, and bronchial epithelial hyperplasia were observed in groups A and B. Emphysema was the most common lesion. Bronchopneumonia with abscesses was only observed in group A. Glutathione levels were significantly decreased and malondialdehyde levels were significantly increased in group A. No significant difference was observed in superoxide dismutase levels between the groups. The data presented indicate that before using MMA, adequate protection systems should be in place to prevent occupationally related MMA respiratory-tract injuries.