OBJECTIVES: To evaluate adoption of treatment guidelines recommending the initiation of a DMARD within 12 months of new RA diagnosis and to identify risk factors for non-initiation. METHODS: Newly diagnosed adult RA patients from 2003-2009 with 12 months of continuous enrollment before and after their first RA diagnosis were identified in the MarketScan Research Databases®.  Patients were excluded if they used a biologic or conventional DMARD prior to their first diagnosis.  Patients were categorized as DMARD initiators or non-initiators in the 12 months following diagnosis (follow-up period).  We compared demographic and clinical characteristics of initiators versus non-initiators using Cox-proportional hazard models.  RESULTS: A total of 26,911 patients met the study criteria; 17,014 patients (63%) initiated a DMARD therapy in the follow-up period.  At baseline, compared to initiators, non-initiators were older [mean age 62.6 (SD=14.9) versus 58.1 (SD=13.3), p<0.001], had a higher Deyo-Charlson Comorbidity Index Score (CCI) [0.76 (SD=1.3) versus 0.58 (SD=1.1), p<0.001], were more likely to have had an inpatient stay in the pre-index period (19% versus 13%, p<0.001), had higher pre-index total costs [$12,725 (SD=$24,500) versus $10,534 (SD=$20,259), p<0.001] and had similar out-of-pocket total costs [$1,224 (SD=$1,370) versus $1,230 (SD=$1,519), p=0.738)] and out-of-pocket outpatient pharmacy costs [$492 (SD=$611) versus $478 (SD=$553), p=0.052].  Multivariate-adjusted risk factors for DMARD non-initiation included older age (85+), high CCI (3+), and the presence of GI disorders, cardiac conditions, hypertension, osteoarthritis, or respiratory infections in the pre-index period.  Patients who used an NSAID or corticosteroid, were diabetic, saw a rheumatologist, or had a rheumatoid factor test in the pre-index period were all more likely to initiate a DMARD in the follow-up period. CONCLUSIONS: The majority of new RA patients followed treatment guidelines and initiated a DMARD therapy; nevertheless, over one-third of the patients did not initiate DMARD therapy within a year after diagnosis.