We propose to add a collection of genetic material to a clinical trial of anti-oxidant supplementation for the amelioration of asthma in 7-12 year olds being conducted at a public pediatric hospital in Mexico City. The anti-oxidant study has been approved by the Institutional Review Board of the National Institute of Public Health in Mexico City and is scheduled to begin in September 1998. The purpose of this add-on study is to examine genetic polymorphisms that may be related to asthma. Asthma cases will be compared with their parents as controls. In partaicular, we will save the buffy coat from the blood collection being done on the asthmatic child for measurements of plasma micronutrients in the anti-oxidant trial for extraction of DNA. This part of the sample would otherwise be discarded. In addition, we will enroll the parents of the asthmatic child as controls for the child. From the parents, either a 10 ml blood sample or if they prefer, a sample of buccal cells will be collected. Although our current plan is to compare the asthmatic child to the parents using statistical methods based on the "transmission disequilibrium test" because research into various family designs for candidate gene studies is rapidly evolving and various sibling control sample strategies have been discussed, we would also like to collect a genetic sample on as many of the child's siblings as possible with priority given to those closest in age. This will enhance the future usefulness of the samples. We anticipate enrolling approximately 200 families.