Four tests for the evaluation of lead poisoning are reviewed from both the clinical and methodological aspects. Whole blood or erythrocyte lead measurements appear to provide the best means of assessing the bodily burden of lead with electrothermal and Delves cup flame atomic absorption spectorphotometric techniques providing accurate and precise results. Urine lead is less reliable as a screening test for lead poisoning but is excellent for monitoring the course of ethylenediamine tetraacetic acid (EDTA) therapy. Atomic absorption methods for urine are made difficult by the variable matrix of urine but satisfactory electrothermal and flame procedures have been described. Erythrocyte delta-aminolevulinic acid dehydratase activity is a very sensitive index of lead exposure,--perhaps too sensitive. Analytical procedures for measuring this enzyme are subject to errors and many complicating factors such as lack of stability of the specimen limit the usefulness of the test. Urine delta-aminolevulinic acid is of questionable value as a screening procedure and also is subject to analytical problems.