To study the features of multiple sclerosis (MS) with child age-at-onset, we examined 254 patients with confirmed diagnosis of MS. The disease developed at the age younger than 16 years in 27 patients. A control group included 303 healthy volunteers. Correlations between the rate of disease progression and the age-at-onset were found. The more benign course of MS was noted in patients with earlier disease onset. There were more women and the disease frequently manifested with retrobulbar nephritis in the group with early onset. The results indicated that a G allele of -308G/A polymorphism of the TNF-α gene might be a risk factor for MS. The A allele may play a protective function. No association between -137G/C IL-18 polymorphism and MS was found. These polymorphisms did not contribute to the predisposition to early onset of MS.