The genetic test is gradually replacing probe drugs as the primary tool for screening populations for the CYP2C19 polymorphism. A full appreciation for the clinical and toxicological relevance of this genetic variation is presently limited. Further research is needed in several areas. The development and use of 3-D models of the CYP2C19 enzyme to automate and increase the rate at which CYP2C19 substrates are identified could reap great benefits. Meanwhile, clinical research should begin to determine whether the CYP2C19 polymorphism affects therapeutic outcomes and toxicity of drugs in actual patient settings. Combining research efforts in molecular modeling, genetic testing, clinical and epidemiological research will be required if better appreciation of this genetic variation and its importance in the population at large is to emerge.