Probability theory evaluates among other things the relative frequency with which an event (like rain or an earth quake) occurs or is likely to occur. This book of problems has been designed to accompany an undergraduate course in probability. The only prerequisite is basic algebra and calculus. Each chapter is divided into three parts: Problems, Hints, and Solutions. The hints, a feature, frequently absent in textbooks, is crucial in teaching mathematics and will make this book particularly useful for self-study.