BACKGROUND: Despite the availability of effective hypertension, hyperlipidemia, and hyperglycemia therapies, target levels of systolic blood pressure (SBP), LDL-cholesterol (LDL-c), and hemoglobin A1c control are often not achieved. OBJECTIVE: To examine the relative importance of patient medication nonadherence versus clinician lack of therapy intensification in explaining above target cardiovascular disease (CVD) risk factor levels. DESIGN: Cross-sectional assessment. PARTICIPANTS: In 2005, 161,697 Kaiser Permanente Northern California adult diabetes patients were included in the study. MEASUREMENT: ‘Above target’ was defined as most recent A1c >/=7.0% for hyperglycemia, LDL-c >/=100 mg/dL for hyperlipidemia, and SBP >/=130 mmHg for hypertension. Poor adherence was defined as medication gaps for >/=20% of days covered for all medications for each condition separately. Treatment intensification was defined as an increase in the number of drug classes, increased dosage of a class, or a switch to a different class within the 3 months before or after notation of above target levels. RESULTS: Poor adherence was found in 20-23% of patients across the 3 conditions. No evidence of poor adherence with no treatment intensification was found in 30% of hyperglycemia patients, 47% of hyperlipidemia patients, and 36% of hypertension patients. Poor adherence or lack of therapy intensification was evident in 53-68% of patients above target levels across conditions. CONCLUSIONS: Both nonadherence and lack of treatment intensification occur frequently in patients above target for CVD risk factor levels; however, lack of therapy intensification was somewhat more common. Quality improvement efforts should focus on these modifiable barriers to CVD risk factor control.