It has been suggested that an insertion/deletion (I/D) polymorphism in intron 16 of the angiotensin-converting enzyme (ACE) gene may be associated with diabetic nephropathy The aim of this study was to investigate whether an association exists between ACE I/D polymorphism and glomerular filtration rate (GFR) in type 2 diabetes mellitus. A total of 128 type 2 diabetic patients were included in the study with the following ACE genotype distribution: DD 40, ID 58,11 30. I/D polymorphism was determined by polymerase chain reaction (PCR). Mean GFR was not statistically different according to ACE genotype (DD: 89.9 +/- 28.1 ml/min, ID: 99.5 +/- 25.1 ml/min, II: 96.6 +/- 19.6 ml/min). There was no significant difference in genotype distribution in normo-, micro- and macroalbuminuric patients (DD:ID:II [%], normo- 35:46:19, micro-28:55:17, macro- 31:55:14). ACE I/D polymorphism does not seem to be associated with GFR in type 2 diabetic patients.