This is the first study to investigate the association between HNF1A gene SNPs rs1169288 (encoding HNF1A p.Ile27Leu), rs1800574 (encoding HNF1A p.Ala98Val) and rs2464196 (encoding HNF1A p.Ser486Asn), and having early-onset, MODY-like diabetes in the Turkish population. This evidence concerns the gene HNF1A and diabetes mellitus.