Objective. This study was conducted to analyze the effect of certain environmental factors on clinical and laboratorial variables in a cohort of multiple sclerosis patients. Material and methods. Serum vitamin 25(OH) D, smoking habits and oral contraceptive use were evaluated in 36 relapsing-remitting MS female patients between ages 29-45 under Interferon beta-1a therapy. Clinical variables included annualized relapse rate and Expanded Disability Status Scale (EDSS). The effect of sun exposure,

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... dietary and smoking habits and oral contraceptive use on 25(OH) D levels was also examined. Results. Patients with higher 25(OH) D serum levels and consumers of oral contraceptives (OC) had better clinical outcomes, but not in a statistically significant extent. The practice of artificial tanning, consumption of alternative sources of vitamin D (cod liver oil, omega-3 fatty acids) and the use of oral contraceptives were associated with significantly higher vitamin D levels. Conclusions. Smoking seems to have less effect on disease progression and vitamin D levels than anticipated. Oral contraception use could be benefic and maintaining a high plasma D level is also encouraged in MS patients.