The analysis of the revenues and expenses of the Social Insurance Fund was conducted in the paper. The revenues sources and their determinants, including number of the insured, were presented. While discussing the expenses, special attention was paid to the number of beneficiaries and the level of benefits. Between 1999 and 2012, the growth of revenues was higher than the growth of expenses. The proceeds of the SIF mostly came from the contributions, and the funds were generally allocated to the payment of benefits. In the analysed period, contribution revenues did no fully cover the SIF expenses.