Four different composite resins (three small particle and one microfill) were placed in 106 posterior teeth and followed over a five-year period. Colour and marginal discoloration characteristics were assessed from standard photographs, and wear evaluated by standardized measurement of cavity wall exposure and scanning electron microscopy of replicas. The colour of the materials changed, but not to an unacceptable degree, over the five-year period, and marginal discoloration increased slightly. The wear rate of the four materials was similar, and appeared to decrease after about 2-4 years. Some materials exhibited surface damage, and some of the microfill restorations failed catastrophically.