In order to improve the vibration characteristics of a spindle cover made of 2 mm thick steel plate for high speed machine tools, the cover was reinforced with carbon fiber epoxy composite material. Considering the mounting conditions and the vibration mode shape of the spindle cover, the stacking sequence and the thickness of the reinforced composite laminate were determined through finite element analysis. The relationship between the loss factor and the stacking sequence was also investigated. The steel-composite hybrid spindle cover was fabricated by co-cure bonding in an autoclave and its dynamic characteristics were tested. From the tests, it was found that damping improvement of the composite hybrid spindle cover was substantial over a wide frequency range. (C) 2001 Elsevier Science B.V. All rights reserved.