Values of collision efficency and scavenging rates for drops interacting with aerosol particles are presented using more accurate flow fields than previous work and for a much greater number of drops than hitherto obtained. All calculations are performed at an ambient temperature of 10 degrees C and atmospheric pressure of 900mb. Computations of collision efficency are performed for a drop radius range from 50 to 500 micrometre (um), for particle radius from 0.005 to 10um, for relative humidity values of 50,75,95 and 100% and for particle density of 1,1.5,2.0 and 2.5 x 10^3 kg m^-3. In addition the collision effiicency was also calculated fro elctric charges on the drop and particle and for an electric field, representive of typical thundercloud values. Combined use is made of a rigorous trajectory model together with a flux model and comparision is made between them in the overlap size region . Precipitation scavenging rates and the percentage of aerosol particles scavenged by precipitation drops described by Marshall-Palmer size distribution is also calculated.