Diabetes mellitus (DM) has been well known to be one of the risk factors of coronary artery disease (CAD). Recently, remnant-like particles cholesterol (RLP-C) has been reported to be associated with CAD. However, few studies reported the association of RLP-C level with CAD in subjects with DM. To investigate the effects of presence or absence of DM on the association between RLP-C and CAD, we compared the RLP-C level in 142 male patients with CAD and 123 male subjects without CAD (non-CAD), including 44 and 38 DM patients, respectively. RLP-C was significantly higher in CAD than non-CAD (P<.05). RLP-C and RLP-C/plasma-triglyceride (TG) ratio in CAD with DM were higher than CAD without DM (P<.01, P<.05), and non-CAD with DM (P<.001, P<.05). There was positive correlation between RLP-C and plasma-TG in non-CAD without DM (r=.44, P<.01), non-CAD with DM (r=.56, P<.001), CAD without DM (r=.81, P<.0001), and CAD with DM (r=.75, P<.001). After excluding the hypertriglyceridemic patients (>200mg/dL), RLP-C/plasma-TG ratio was significantly higher in CAD with DM than CAD without DM (P<.001) and non-CAD with DM (P<.05). These results suggest that increased RLP-C to plasma-TG may be associated with CAD in middle-aged diabetic male subjects. Copyright (C) 2001 by W.B. Saunders Company.