This research (which is the second phase of a study intended to provide reliable information on fatigue behavior of steel bridge members), and an extensive investigation of fatigue effects in welded steel beams, which formed the basis for recommendations for revision of the fatigue provisions of the AASHP Standard Specifications for Highway Bridges. A hundred and fifty seven steel beams and girders were fabricated and tested to define the fatigue strength of various structural details, including stiffeners and attachments. Stress range was observed for nearly all the variation in cycle life for all stiffener and a attachment details examined in this study.