ALSPAC has contributed to a large number of genomewide association studies (GWAS). We have these data imputed to the recent reference panels for 9,321 mothers and 9,115 children (1000 genomes) and recently to the latest release of the 1000 Genomes (B2710). There is a further requirement to impute this data to the Haplotype Reference Consortium (HRC), a much larger reference panel of over 60,000 haplotypes to contribute to ongoing international GWAS studies. Furthermore, imputation can vary in quality according to imputation algorithm. Imputation using the MACH algorithm will bring ALSPACs HRC imputed data in line with other large genetic studies.