Fatigue crack growth from surface planar defects is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, ship hulls and other various structures. The authors reported previously a preliminary analysis on fatigue crack growth from a single surface flaw⁷⁾ . The present study attempts to apply the same approach to some practical or general problems such as the estimation of crack growth life to penetrate the plate thickness, analysis on the interaction of multiple cracks etc. An experiment on the coalescence of two cracks was carried out under cyclic plane bending condition as a first attempt to the analysis of multiple crack problems. It is noted that the crack shape change is well characterized by the analogy to that in a single crack growth. A simplified formulation is proposed to characterize the interaction effect of adjoining cracks on the crack growth rate.