Multivariable regression analysis has been applied to fatigue life prediction of three types of welded joints based on literature search of S-N data. Joint details include butt joints, cruciform joints and longitudinal attachments. Variables considered are stress range, stressed plate thickness and loading mode. Thickness effect regarding stressed plate thickness is re-established for three types of joints in order to check its relevance to fatigue life before moving into multivariable regression. Linear fatigue life estimate equations are derived for all three types of joints considering plate thickness and loading mode. Fatigue life predictions by equations are compared and discussed with chosen test results from literature. Four case studies are chosen fromliterature search and different fatigue life prediction methods are used to compute estimated fatigue lives. Results from different methods are compared and discussed with test results. Case studies include 2mm and 6mm thick symmetrical longitudinal attachments, 12.7mm unsymmetrical longitudinal attachment, 38mm symmetric longitudinal attachment under bending and 25mm and 38mm load-carrying cruciform joint under bending. Case studies are modelled as close to test specimens as possible. Fatigue life prediction methods include hot-spot method where structural hot-spot stress is obtained through two linear surface extrapolation methods, quadratic surface extrapolation and through thickness integration at the weldtoe. Effective notch method and fracture mechanics methods are applied for cruciform joint.