['The common variants p.I27L (rs1169288), p.A98V (rs1800574) and p.S487N (rs2464196) of the hepatocyte nuclear factor 1-α (HNF1A) gene have been inconsistently associated with impaired glucose tolerance and/or an increased risk of type 2 diabetes mellitus (T2DM). The present study aimed to investigate whether these associations are affected by weight.', 'A cross-sectional analysis was conducted among 861 Japanese subjects (males: 65.5%; 61.8±12.3years) attending a health-screening programme. Interactive effects between HNF1A variants and weight status on risk of T2DM or dysglycaemic status were determined.', 'The 27L variant carriers were at higher risk of T2DM and dysglycaemic status than non-carriers, but only in normal-weight subjects [odds ratio (OR): 2.04, P=0.03 and OR: 2.56, P=0.01, respectively]. An interactive effect of the p.I27L (rs1169288) variant and weight status on the risk of dysglycaemic status was found (P=0.04). Age, but not body mass index (BMI), was a risk factor for dysglycaemic status in the 27L carriers (OR: 1.05, P=0.0003), whereas BMI was a risk factor in non-carriers (OR: 1.23, P=0.008). No carriers of 98V were identified, and 487N was not associated with either T2DM or dysglycaemic status in our study population.'] Are associations between the common HNF1A gene variant p.I27L ( rs1169288 ) and risk of type 2 diabetes mellitus influenced by weight?