The alterations in atherogenic index of plasma (AlP) in type 2 diabetic patients and their normoglycemic first-degree relatives (NFDR) were investigated, and the effects of Acarbose or Glimepiride on AIP in 99 type 2 diabetic patients were evaluated. Triglycerride (TG), total cholesterol, high density lipoprotein-cholesterol (HDL-C) levels were analyzed, and Log (TG/HDL-C) was calculated as AIP in 62 type 2 diabetic patients and their 67 NFDR from 29 type 2 diabetic pedigrees and in 45 healthy controls without family histories of diabetes. Also analyzed were the same parameters in 99 type 2 diabetic patients before and after therapy with Acarbose or Glimepiride. The results revealed that diabetic patients and their NFDR had significantly higher AIP than did the controls, whereas no significant differences were seen between diabetic patients and their NFDR. Positive correlation of AIP between type 2 diabetic patients and their offspring were observed (r = 0.241, P < 0.05). After 8 weeks therapy with Acarbose, the AIP of type 2 diabetic patients was decreased significantly, and no differences were observed for AIP levels in Glimepiride group although the AIP was lower when compared with the untreated level. As a significant inverse correlation of small dense low density lipoprotein (sdLDL) with AIP was confirmed, our data suggest that diabetic patients and their NFDR from type 2 diabetic pedigrees had significantly higher AIP than did controls; AIP could be decreased by therapy with Acarbose in type 2 diabetic patients; Glimepiride may bring potential benefit to type 2 diabetic patients by influencing sdLDL.