The purpose of this task order is to provide all services needed to conduct the second follow-up of the entire GuLF STUDY cohort, to validate selected health endpoints (e.g. via medical records) identified in Phase 1 follow-up and prospectively during Phase 2 follow-up, and to evaluate biological effects of oil-spill exposures. Cohort follow-up will include tracing of participants, subcontracting for, and training and supervising telephone center staff, implementing a computer assisted telephone interview, operating a call center and hotline, providing remuneration as needed to maximize participation, and carrying out on-the ground locating for priority participants living in specific Gulf state regions or having higher and more informative exposures.