If a is not a multiple of « and a"~ ' * 1 mod n, then n must be composite and a is called a "witness" for «. Let F(n) denote the number of "false witnesses" for n, that is, the number of a mod n with a"-1 s l mod «. Considered here is the normal and average size of F(«) for « composite. Also considered is the situation for the more stringent Euler and strong pseudoprime tests.