Apolipoprotein B (apoB) and nonHDL-cholesterol (nonHDL-C) are cardiovascular disease (CVD) risk markers, although data in adults with type 1 diabetes mellitus (DM) are limited. We hypothesized that elevated apoB and nonHDL-C would be associated with greater odds of coronary artery calcification progression (CACp), a measure of coronary atherosclerosis, than either category alone in adults with type 1 DM. We grouped subjects with type 1 DM (n=652) into four groups; elevated apoB (≥90mg/dL) and elevated nonHDL-C (≥130mg/dL), elevated nonHDL-C alone, elevated apoB alone, and normal apoB and nonHDL-C. We employed logistic regression to examine the associations between the groups and CACp over 6-years. We performed sensitivity analyses with elevated apoB and nonHDL-C re-defined as ≥ cohort means (91.4, 119.0 mg/dL respectively). Subjects with elevated apoB and nonHDL-C had greater odds of CACp compared to subjects with normal apoB and nonHDL-C (OR: 1.90, 95% CI 1.15-3.15), and compared to subjects with elevated apoB alone (OR: 2.86, 95% CI 1.43-5.74) adjusting for age, sex, duration, HbA1c and statins. Similar results were obtained with elevated apoB and nonHDL-C defined as ≥ the cohort means. In conclusion, elevated apoB and nonHDL-C carry a greater risk of atherosclerosis than elevated apoB in the absence of elevated nonHDL-C in adults with type 1 DM. These data suggest that apoB and nonHDL-C should be viewed as complementary rather than competitive indices of CVD risk in type 1 DM.