OBJECTIVE: To evaluate the influence of inadequate glycemic control (IC) in comorbidity and health resource utilization of type 2 diabetic patients treated in a general practitioner setting. METHODS: Retrospective observational study (systematic-sampling) of patients older than 18 years, treated in 5 primary care centres during 2005. The following parameters were evaluated: IC, defined by HbA1c>7%; age; sex; comorbidities (hypertension, hypercholesterolemia, smoking, obesity, ischemic-heart-disease, cardiovascular event (CVE), COPD, depression, cardiac-renal-hepatic insufficiency, microvascular complications); clinical parameters (BMI, total-cholesterol, LDL-Friedewald, HDLc, glucose, triglycerides); and resources utilization (specialist referrals, medical visits, drugs, tests). A logistic regression analysis was used to correct the model (IC as the dependent variable). Costs were contrasted by a multivariate ANCOVA analysis with marginal means estimation (Bonferroni-adjust), using SPSS 12.0 and a statistical significance of p<0.05. RESULTS: 5,014 patients were evaluated; mean age was 64.6± 12.1; 50.3% were men; 16.1% had a history of a CVE and 27.4% had IC (CI95%:26.2-28.6%). Suffering a CVE (OR=1.2; CI95%:1.0-1.4; p=0.021), smoking (OR=1.2; CI95%:1.0-1.4; p=0.017) and retinopathy (OR=1.5; CI95%:1.3-1.7; p=0.000) were independently related with IC. Clinical parameters and resources utilization were different in IC vs. good control patients: glucose 181.7±61.8 vs. 129.1±32.0mg/dl (p=0,000); LDLc 122.4±38.0 vs. 119.7±35.48mg/dl (p=0.018); mean number of oral antidiabetics was 1.3±0.8 vs. 1.2±0.6 (p=0.002); and insulins 0.5±0.6 vs. 0.1±0.4 (p=0.000). Total cost/patient/year adjusted with covariance was 1.953.86€ (EE=73.7) in patients with inadequate control versus 1.747.48€ (EE=36.2) with good control (p=0.03). The pharmaceutical cost represents a 74.2% overall resources utilization costs in both good and inadequate controlled patients. CONCLUSIONS: Smoking, CVE and retinopathy were independently related with inadequate glycemic control. Uncontrolled diabetic patients have a worse lipid profile and a higher glucose level despite a higher use of oral antidiabetics and insulin, and represent a higher cost/patient/year. General practice centres should promote specific interventions to improve glycemic control in diabetic patients.