This paper presents the results of a comparative experimental study on the fatigue performance of two types of side longitudinal stiffeners in tankers. One is an inverted angle stiffener supported by a soft-toed web stiffener with a soft-toed backing bracket. The other is a T-type stiffener supported by a flat bar web stiffener without a backing bracket, as an alternative to the angle type stiffener. Six full-scale structural models (three for each type) were tested under fully-reversed constant amplitude cyclic loading, resulting in fatigue lives ranging between about 5x10(4) and 2x10(6) cycles. Crack growth data as observed on the surface are presented and discussed. Finite element analyses were also conducted to evaluate the two types of longitudinals based on calculated hot spot stress. Overall, the T-type longitudinal stiffener showed superior fatigue performance.