The objective of access path optimization in relational joins is to minimize the number of pages accessed in performing a join, since the cost of data retrieval from disk accounts for most of the join processing costs. We develop an efficient approach to access path optimization by modeling an access path as a tree traversal process. Two join algorithms are developed using this model. The access path is stored as a compact index relation, which requires absolutely minimal storage. The join is easily materialized by reading the index relation sequentially, and performing the operations coded in its tuples in their serial order. The proposed approach is shown to result in globally minimal page accesses in certain classes of joins. Using a detailed probabilistic analysis and computational study, the proposed approach is shown to be much superior to the state-of-the-art join optimization methods for a general class of joins. INFORMS Journal on Computing, ISSN 1091-9856, was published as ORSA Journal on Computing from 1989 to 1995 under ISSN 0899-1499.