Occurrence of microorganisms isolated from clinical specimens collected from patients in Clinical Hospital no. 1 in Gdańsk in years 1997-1999 was analyzed. In this period there was no change in occurrence of Gram-negative bacteria, that accounted for 44-46% isolates. The number of isolations of Gram-positive bacteria dropped from 45% to 40%, and yeast risen from 5% to 10%. The analysis of blood cultures shows decrease in occurrence of bacteremia caused by Gram-negative bacteria and increase in occurrence bacteremia caused by Gram-positive bacteria and yeast. We observed also that the number of multi-resistant Gram-positive isolates (MRSA, VRE) decreased but there was rise in occurrence of multiresistant Gram-negative isolates (ESBL+, CRPA).