Pharmacogenetic studies of drugs used in the treatment of asthma have produced a few examples of reduced response in patients carrying specific genotypes in genes involved in the action of beta-2 agonists or leukotriene modifiers. Other candidate genes related to these drugs, as well as glucocorticoids, theophilline, anticholinergics, antihistaminics, and drug-metabolizing enzymes, may be proposed. Statistical power and population stratification may be issues of importance in case-control association studies. Future developments include expanded gene knowledge from asthma genetic and genomic studies, the development of new preventive and curative treatments, multiple contemporary genotyping methods for pharmacogenetically important genes in a given individual, and the construction of asthma functional pharmacogenomic profiles. In conclusion, it seems that asthma pharmacogenetic studies need to be replicated in prospective clinical trials in different populations with a large number of subjects being genotyped. It is suggested that large clinical trials which are proposed for asthma drugs experimentation should include a pharmacogenetic study as well.