Abstract: It is well known that design and analysis for the ultimate load carrying capacity of a st ructure made of isot ropic materials can be accomplished only based on a st ress failure criterion (e. g. the first or the fourth st rengththeory int roduced in a mechanics of materials text book) . This is , however , not t rue for composites in general. It ispointed out in the paper that the ultimate failure of laminated composite beams subjected to bending cannot be figured out only based on a st ress failure criterion. Thus , the design and analysis for the ultimate load carrying capacityof composite st ructures require not only a st ress failure criterion but also a critical deformation related condition. Toshow this , some experimental evidences are summarized in the paper. Another purpose of this paper is to presentsome latest result s achieved by the authors in the relevant research areas especially in determination of the ultimatebending st rength of laminated composites. A number of challenging topics are also addressed in the paper.