The paper presents measurements of PM emission in the exhaust gas of a gasoline fueled SI engine alternatively fueled with LPG. The research was performed on a 170.A1 engine using the Dekati ELPI+ PM analyzer and Micro Diluter 6100 (a micro-dilution tunnel). The author also measured the concentration of exhaust gaseous components with the use of Horiba MEXA 1500GH analyzer. The author compared the PM concentration and size distribution in the exhaust gas for both fuels.