A miniature sandwich specimen was employed to determine the influence of matrix modulus and fiber-matrix interfacial bond strength on composite compression strength. This specimen generates significantly higher compression strengths for unidirectional carbon/ epoxy composites compared to conventional coupons and also exhibits a smaller scatter of the data. The matrix modulus of AS4/3501-6 and AS4/APC-2 composites was varied by testing specimens over a range of temperatures. In both composites, compression strength increases with matrix shear modulus up to a critical value of the shear modulus, above which it remains constant. At low matrix shear moduli, failure initiates via fiber microbuckling, while at high shear moduli, failure is dominated by the fiber compression strength. The influence of the fiber-matrix bond strength was investigated with epoxy composites reinforced with two different carbon fibers having treated and untreated surfaces. Composite compression strength varied directly with the 90° tensile strength, which was adopted as a measure of relative interfacial bond strength.