The Mathematical Association of America is pleased to publish this sequel to NML vol. 27; it contains the International Mathematical Olympiads, 1978–1985, and forty supplementary problems selected by Murray S. Klamkin, who prepared this text. The educational impact of such problems in stimulating mathematical thinking of young students and its long range effects have been eloquently described, both from the viewpoint of the participant and that of the mature mathematician in retrospect, by Gábor Szegö in his preface to the Hungarian Problem Books, volumes 11 and 12 of this NML series.

Our aim in all problem collections of this series is not only to help the high school student satisfy his curiosity by presenting solutions with tools familiar to him, but also to instruct him in the use of more sophisticated methods and different modes of attack by including explanatory material and alternate solutions. For problem solvers, each problem is a challenging entity to be conquered; for theory spinners, each problem is the proof of their pudding. It is the fruitful synthesis of these seemingly antithetical forces that we have tried to achieve.

We are extremely grateful to Murray S. Klamkin, the dedicated coach and expert problem solver, for having compiled the solutions to all the problems. The editors enjoyed their task and gratefully acknowledge Peter Ungar's elaborations, addenda and applications of some solutions.