The Rohm and Haas Company's Toxicology Laboratory currently is conducting for MPA an inhalation developmental toxicology study in rats involving methyl methacrylate. The study's protocol involves using 225 Crl: CD BR female rats and 125 of such male rats to obtain five groups of 125 pregnant females (25 presumed-pregnant females per group). Thereafter, the mean Day 0 gram body weight for each of the five groups is calculated. If statistically significant differences exist between groups, the protocol calls for switching before exposure begins. Dams showing signs of illness are to be discarded before treatment begins. With one of the five groups serving as a control, the other four groups are exposed by inhalation to MMA for six hours per day from gestation day 6 through 15. Body weight, clinical signs and feed consumption are evaluated during the exposure period and beyond up to gestation day 20. Following these procedures, the protocol requires that the dams be sacrificed for analysis. Any animals suffering a spontaneous death during the study will also be examined.