The proficiency testing of crime laboratories began in the mid-1970's and currently assumes an important role in quality assurance programs within most forensic laboratories. Beginning in 1978, a fee-based crime laboratory proficiency-testing program was launched and has grown to it present level of approximately 400 laboratories worldwide. This is the first of two articles that review the objectives, limitations, and results of this testing from 1978 through 1991. Part I reviews the success of laboratories in the identification and classification of common evidence types: controlled substances, flammables, explosives, fibers, bloodstains, and hairs. Laboratories enjoy a high degree of success in identifying drugs and classifying (typing) bloodstains. They are moderately successful in identifying flammables, explosives, and fibers. Animal hair identification and human-hair body-location results are troublesome. Part II (See NCJ-159179) will review the proficiency of crime laboratories in determining whether two or more evidentiary samples shared a common origin. 12 tables and 52 references