The history of asbestos use and asbestos-related disease is replete with comments that the public health would have been better protected if the results of laboratory investigation, epidemiologic surveys, and clinical studies were made available at appropriate intervals during the ongoing research, rather than in the generally accepted method of awaiting completion of studies prior to reporting medical and scientific findings. No substantive evidence of long-term adverse effects has been published in workers exposed to man-made vitreous fibers. Nevertheless, in an effort to preclude a repetition of this error of omission that occurred with asbestos exposure and use, the Thermal Insulation Manufacturers Association is regularly reporting interim and final data from ongoing animal studies. A significant segment of man-made vitreous fibers have now been tested in state-of-the-art chronic studies. This paper includes the recently completed animal inhalation studies on refractory ceramic fibers and fibrous glass. It also reviews interim data on mineral wool studies.