The ZFP36 gene codes for TTP, a regulator of TNF alpha. In mice, TTP deficiency results in a systemic autoimmune inflammatory syndrome with severe arthritis. We hypothesized that genetic variations in ZFP36 are associated with autoimmune disease in humans. The primary objective of this study was to identify human ZFP36 genetic variants in autoimmune disease cases and controls, determine their frequencies in a general clinic population, and construct haplotypes. We resequenced ZFP36 in 316 individuals with autoimmune diseases and identified 28 polymorphisms and determined the frequency of all the known ZFP36 polymorphisms in 484 participants of the Environmental Polymorphism Registry, a regional registry being conducted by the NIEHS. Based on the sequence-verified ZFP36 genotypes, 34 haplotypes were constructed. As a secondary objective, we examined autoimmune disease cases and controls for potential ZFP36 genetic associations. One novel polymorphism, ZFP36*8, a C to T transition in the protein coding domain, was significantly associated with rheumatoid arthritis (RA) in African-Americans (RR=1.23, 95% CI: 1.11-1.36). The data presented here suggest a tentative association between ZFP36 and RA. This finding, as well as the ZFP36 polymorphisms and haplotypes identified here, should form the basis for future association studies in autoimmune diseases.