The four U.S. presidents who served in office without a vice president were John Tyler, Millard Fillmore, Andrew Johnson and Chester A. Arthur. Each of these four men were vice presidents succeeding presidents who died in office at a time when no constitutional provision existed for choosing a vice-presidential successor.
John Tyler served as vice president under William Henry Harrison who died weeks after taking office in 1841. Tyler finished Harrison's term and did not run for one of his own. Millard Fillmore succeeded Zachary Taylor after Taylor's death in office and served out the remainder of his term. Andrew Johnson was Abraham Lincoln's second vice president. When Lincoln was assassinated early in his second term, Andrew Johnson succeeded him. Chester A. Arthur completed the term of President James Garfield after he was assassinated in 1881.