In 2003, 87,336 cases of mumps were reported in Poland. The incidence (228,7 per 100,000) was higher then in 2002(104.6), which corresponds to a periodical increase of mumps incidence. According to the natural periodicity the peak incidence would be expected to take place in 2002. The increase of mumps incidence in 2003, still lower however then the previous peaks, can be attributed to the prolongation of the epidemics cycle usually occurring with growing vaccine coverage. Even though the mumps vaccine was not included into the national immunization program, the coverage in 3-year old children in 2003 reached 39.6%. Approximately 4.6% of cases were hospitalized (4,056) and no mumps deaths were reported. Children 5-9 year old constituted the most affected age group (incidence 2,133.1 per 100,000). In Poland the MMR vaccine was recommended on voluntary basis in place of measles vaccine for children in their 2nd and 7th year of age. Immunization of 2-years old children is mandatory beginning in 2004.