Three series of torsional dynamic mechanical analysis (DMA) tests were conducted on unidirectional carbon/epoxy composites to determine differences in interfacial bond strength. For the first series, composites were manufactured with PAN-based and pitch-based carbon fibers. The fibers had a proprietary surface treatment. For the second series of tests, the composites were made with four grades of pitch-based carbon fibers. Two different methods of surface treatment were used on the fibers. As a comparison, short beam shear tests were conducted on the composites made with fibers which had different surface treatments. The final series of tests were conducted on composite samples made from one grade of pitch-based fibers with four different fiber volume fractions. All samples were made using the same matrix material. Dynamic mechanical analysis was able to clearly differentiate between the fiber/matrix bond strength of pitch-based and PAN-based fibers. The interlaminar shear strength correlated well with the DMA results, indicating that DMA can measure the effectiveness of various surface treatments. The dynamic mechanical loss modulus increased with increasing fiber volume fraction or total surface area.