The results of measurements of aerosol samples in the 1998-1999 period in the monitoring network of the ASS-500 stations in Poland are presented. The concentration of ¹³⁷Cs remained at a rather low level during these two years. Higher levels resulting from the Algeciras release in southern Spain were identified in the first week of June 1998 at four stations situated in southern Poland. Higher concentrations of ¹³⁷Cs were also observed during some other weeks of the presented period, but their origin has not been identified. The radionuclides of natural and antrophogenic origin were at their normal levels of activity. For comparison, the results from some other European stations are presented.