The aim of the practice is learn methods for the investigation of the influence of environmental factors, in particular chemicals from the environment, on the immune system and the development of diseases. Using data from an ongoing epidemiological study (LARS ? Leipzig Allergy Risk children Study) statistical methods will be learned and trained. As an example the influence of maternal chemical exposure during pregnancy on the development of allergic sensitisations and diseases later in childrens life will be investigated. For the LARS study between 1995 and 1996 in Leipzig newborn children at risk of atopy (double positive family atopy history and/or elevated cord blood IgE and/or birth weight between 1500 and 2500g) were recruited. Information on chemical exposure during pregnancy was obtained from questionnaires self-administered by the parents and by the measurement of volatile organic compounds (VOC) in children?s apartments during the first four weeks after birth. After the first, second, third and fourth year of life blood samples were taken during clinical examinations for the measurement of IgE antibodies. Information on allergic diseases was obtained from questionnaires self-administered by the parents and from physicians diagnosis during medical examinations (eczema). The association between chemical exposure and clinical outcomes will be investigated using the statistical method of linear regression. Odds ratios will be calculated to investigate whether chemical exposure may enhance the risk for the development of allergic sensitisation or diseases later in children´s life. The influence of further atopy risk factors like family atopy history, gender, cord blood IgE, season of birth, smoking and a reduced birth weight will be included in the analysis using linear regression models. The aim of the study is to investigate which exposure situation during pregnancy or which chemicals may have an influence of the development of allergic manifestation in children´s life.