Coin Tossing is the problem in which two parties who do not trust each other want to generate a random coin. Quantum communication allows the parties to generate a coin with bias less than ½, which is impossible classically. However even quantum communication cannot guarantee that the bits are perfectly random. Bit string generation is the generalisation of coin tossing when the two parties want to generate a large number n of coins. We discuss the theory of quantum bit string generation and show that much better security is possible than for quantum coin tossing. We also report on an experiment in which a string of bits is generated which more random than is possible classically.