Asthma is a common, complex human disease. Gene discovery in asthma has been complicated by substantial etiological heterogeneity, the possibility of genes of small effect and the concomitant requirement for large sample sizes. Linkage to asthma phenotypes has been investigated most intensively in the 5q chromosomal region, although results have been inconsistent across studies and all studies have had modest sample sizes. One potential solution to these issues is to combine data from multiple studies in a retrospective meta-analysis by pooling either summary statistics or raw data. The International Consortium on Asthma Genetics combined data from 11 data sets (n=6277 subjects) to Investigate evidence for linkage of 35 markers spanning the cytokine cluster on chromosome 5q31-33 to 'asthma' dichotomy and total serum immunoglobulin E (IgE) levels. Chromosome 5q markers typed in different centers were integrated into a consensus map to facilitate effective data pooling. Multipoint linkage analyses using a new Haseman-Elston method were performed with all data sets pooled together, and also separately with the resulting linkage statistics pooled by meta-analytic methods. Our results did not provide any evidence significant at the 5% level that loci confering susceptibility to asthma or atopy are present in the 5q31-33 region; however, there was some weak evidence (empirical P = 0.077) of linkage to asthma affection. This study suggests that loci in 5q31-33 have at most a modest effect on susceptibility to asthma or total serum IgE levels, may not be detectable or present in all human populations and are difficult to detect even using combined linkage evidence from 2400-2600 full sibling pairs.