It is now possible with a reasonable cost to obtain the genotype of individuals across a large number of markers. By relating genotype and clinical measures to the success of treatment, it will be possible to use this information to predict which treatment would work best for each individual. When this was done for smokers with the low quit success genotype, those with low dependence responded better to the 21 mg dose of nicotine replacement patches than the 42 mg dose while those with high dependence responded better to the 42 mg dose than the 21 mg dose.