Both in theory and practice, great attention is paid to the analysis of the pension expenditures level, their determinants, as well as the options for their reduction, whereas the analysis of the revenues level and contributions, as the most significant revenue in contribution-based pension systems, is often neglected. The aim of this paper is to analyse the determinants of the level of contributions for pension and disability insurance in order to identify options for increasing their levels in the pension system of the Republic of Serbia. By using the comparative method, a comparative analysis of data about the trends of the most significant determinants of contribution levels among the European Union Member States and Serbia is performed. Research results have shown that increase in the contribution level for pension and disability insurance in the Republic of Serbia can be achieved by extending the definition of contribution base of employees, increasing the average effective retirement age and increasing the effective population coverage by this insurance. In addition to pointing out the options for increasing the contribution level for pension and disability insurance, the authors also propose the measures which can be applied in order to affect the increase of the contribution level for this insurance and, therefore, the total revenues level of the pension system of the Republic of Serbia.