This paper presents an effect of microstructural parameters on the mechanical properties in filament-wound unidirectional carbon-epoxy laminate. It is shown that there exists big difference between theoretical prediction using mixture''s rule and experimental values in both of the failure strength and Young''s modulus. This is not only due to the low volume fraction of fibers, but also particularly to the irregular dispersion of fibers throughout the thickness of laminate. As a result, in case of sepcimen with V_f=43%, the experimental strength at failure shows about 44% drop. Similar results are obtained in small filament-wound pressure vessel which has been tested by hydroburst. It is also shown that failure modes are strongly dependent on both the fiber volume fraction and the thickness of test specimen.