This guide covers and describes the factors that influence laboratory immersion corrosion tests, particularly mass loss tests. These factors include apparatus, sampling, test specimen, test conditions (test solution composition, temperature, gas sparging, fluid motion, solution volume, method of supporting test specimens, duration of test), methods of cleaning test specimens, imterpretation of results, and calulation of corrosion rates. This guide also emplasizes the importance of recording all pertinent data and provides a checklist for reporting test data.