The Lifeways Cross-Generation Cohort Study was first established in 2001 and is a unique longitudinal database in Ireland, with currently over three and a half thousand family participants derived from 1124 mothers recruited initially during pregnancy, mainly during 2002. The database comprises a) baseline self-reported health data for all mothers, a third of fathers and at least one grandparent b) clinical hospital data at recruitment, c) three year follow-up data from the families' General Practitioners, and d) linkage to hospital and vaccination databases. Data collection for the five-year follow-up with parents is underway, continuing through 2007. Because there is at present no single national/regional health information system in Ireland, original data instruments were designed to capture data directly from family members and through their hospitals and healthcare providers. A system of relational databases was designed to coordinate data capture for a complex array of study instruments and to facilitate tracking of family members at different time points.