Specimens of similar nominal thickness from commercially available nitrile and neoprene gloves were each tested for breakthrough time against three chemicals. The null hypothesis was that the breakthrough times for the glove specimens of the same generic type but produced by different manufacturers would be the same. Breakthrough time data for each material/chemical combination were analyzed using an analysis of covariance to adjust for differences in the measured specimen thickness while testing for product differences. A significant difference in chemical breakthrough times was found among generically similar products produced by different manufacturers. The largest difference between the mean breakthrough time of two generically equivalent products, 30 vs. 300 min, was obtained for perchloroethylene through nitrile products. In conclusion, breakthrough time data for use in selection of chemical protective clothing or in prediction modeling for chemical protective clothing should be manufacturer and product specific.