The terminal settling velocity of spherical particles was experimentally investigated in cylindrical columns in the range of Reynolds numbers 2 less than or equal to Re-t infinity less than or equal to 185 and of particle-to-column diameter ratios, lambda, about 0.1 to 0.9. It was observed that none of the existing equations relating the terminal settling velocity, u(t), to the diameter ratio, lambda, is fully satisfactory. For this reason two new empirical calculation methods are proposed which enable the determination of u(t) in the whole range of both Reynolds number, Re-t infinity, and diameter ratio, lambda.