The results of J. Širáň and the first author (Australasian J. Combin. 10 (1994)) are generalized, and new formulas for the number of closed walks of length p or pq, where p and q are primes, valid for all vertex-transitive graphs are found. Based on these formulas, several simple tests for vertex-transitivity are presented, as well as lower bounds on the orders of the smallest vertexand arc-tra...