Aim/hypothesis. This study aimed to investigate if variability in the peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1) gene is associated with Type II (non-insulin-dependent) diabetes mellitus. Methods. The PGC-1 gene was examined in 53 Type II diabetic patients applying single strand conformational polymorphism analysis followed by nucleotide sequencing. Identified variants were genotyped in an association study comprising 483 Type II diabetic patients and 216 glucose-tolerant control subjects. A replication study was done in an additional 201 Type II diabetic patients and 293 glucose-tolerant subjects. Furthermore, a potential interaction between the Pro12Ala polymorphism of PPAR-γ2 and the PGC-1 Gly482Ser variant on risk of Type II diabetes was investigated. Results. A total of seven variants (Ser74Leu, IVS2 + 52C→A, Thr394Thr, Asp475Asp, Gly482Ser, Thr528Thr, and Thr612Met) were identified and investigated in an association study. Six of the variants showed no association with Type II diabetes in the initial study. However, the Gly482Ser polymorphism, was more frequent among Type II diabetic patients (37.0%) than among glucose-tolerant subjects (30.8%) (p = 0.032). In a replication study the difference in allele frequencies of the Gly482Ser variant remained significant (p = 0.0135). The combined study yielded an allele frequency of 37.3% (34.7-39.9) for Type II diabetic patients and 30.5% (27.7-33.4) for glucose-tolerant subjects (p = 0.0007). No interaction between this variant and the Pro12Ala polymorphism of PPAR-γ2 was observed. Conclusion/interpretation. A widespread Gly482Ser polymorphism of PGC-1 is associated with a 1.34 genotype relative risk of Type II diabetes.