The objectives of this exploratory case-control study were to evaluate whether genetic polymorphisms of selected Phase I and II metabolizing enzymes are associated with the risk of developing primary esophageal adenocarcinoma, and to investigate potential associations between genotypes and p53 tumor suppressor gene alterations. Cases comprised 45 patients with surgically resected esophageal adenocarcinomas, defined according to strict clinico-pathologic criteria. PCR-based assays (RFLP/SSCP) were used to genotype cytochrome P450 (CYP) 1A1 [MspI; Ile:Val], microsomal epoxide hydroxylase (mEH) (fast and slow alleles), and glutathione S-transferase (GST) T1, M1 and P1. Healthy controls (n=45) from the same geographic region were matched for age, gender and smoking history. For GSTP1, the Ile/Val (a/b) and Val/Val (b/b) variants were seen at increased frequency in cases compared to controls (49% versus 27% and 15% versus 9%, respectively), although these differences achieved only borderline statistical significance (P=0.09). For mEH (exon 3), the presence of the Tyr polymorphism (slow allele) was reduced in cases (42%) compared to controls (53%; P=0.05). Predicted high mEH activity was seen more frequently in cases than controls (OR, 2.2; 95% CI, 0.7-7.3). Polymorphism frequencies for GSTT1, GSTM1, and CYP1A1 were not statistically different between cases and controls. Cases with the GSTT1 null genotype had tumors with altered p53 more frequently than did cases with the common form of GSTT1 (25 versus 6%, respectively; P=0.08). We conclude that polymorphisms of GSTP1 and mEH may be implicated in individual susceptibility to esophageal adenocarcinoma, possibly as a result of increased Phase I activation (mEH) and impaired Phase II detoxification (GSTP1). GSTT1 may also play a role in esophageal tumorigenesis through a pathway that involves abnormalities in the p53 tumor suppressor gene.