Practice standards in medical genetics provide an implicit guide to the ethical, legal, and social implications (ELSI) of genetic tests. The common use of nondirective counseling reflects the principle that many testing decisions should be determined by personal values. Yet geneticists make test recommendations in some circumstances, e.g., RET mutation testing for MEN2 and newborn screening for phenylketonuria (PKU). Conversely, many geneticists recommend against testing for Apolipoprotein E (ApoE) alleles to predict Alzheimer disease (AD) risk. Taken together, these examples suggest that genetic tests can be categorized by a joint consideration of clinical validity and availability of effective treatment for persons who test positive. For genetic tests with high clinical validity/no treatment (e.g., presymptomatic testing for Huntington disease), the predominant concern is adequate nondirective counseling to ensure an informed, autonomous decision. By contrast, the predominant concern for tests with high clinical validity/effective treatment (e.g., PKU) is assuring access to care for eligible persons. For tests with limited clinical validity/no treatment (e.g., ApoE), recommending against test use can be justified on the principle of avoiding harm. For a fourth category, tests with limited clinical validity/effective treatment (e.g., HFE mutation testing for hereditary hemochromatosis), net benefit is the issue: the balance between potential benefits of treatment and potential harms of genetic labeling must be weighed. Where uncertainty exists concerning both clinical validity and effectiveness of treatment, as in the case of BRCA1/2 mutation testing, the value of testing may vary according to different testing contexts. This approach to test categorization allows a rapid determination of the predominant ELSI concerns for different kinds of genetic tests and identifies the data most urgently needed for test evaluation. © 2001 Wiley-Liss, Inc.