Equations of the collision dynamics of a nonspherical particle with a spherical particle are presented. The drag forces and flow fields are calculated by numerical methods, and the superposition technique is used to estimate two-particle interaction. The equations of motion are solved by Gear’s method. A description is included of the computer program NGCEFF (nonspherical gravitational collision efficiency), which allows computation of the shape factor β for collisions between an oblate spheroid and a sphere, based on the above considerations. The results of the nonspherical gravitational collision efficiencies indicate that it is inappropriate to assume that agglomerates collide with the same efficiencies as spherical particles. During the early stages of agglomerate growth, there will be collisions between chain-like particles and spherical particles; the results clearly show that the collision shape factor β is necessary to modify the spherical gravitational collision efficiencies. Representative results for conditions and aerosol materials characteristic of postulated liquid-metal fast breeder reactor accidents are also presented.