This paper examines changes in the audit fees of quoted public limited companies in the UK during the period from 1991 to 1995. After controlling for changes in the size, complexity and risk of auditees, it is shown (based on a logarithm audit fee model) that the audit market experienced a 9.7% reduction in inflation-adjusted fees over this five-year period. The results also provide evidence of overall fee reductions by each of the Big Six. On closer examination, a mixture of fee increases, decreases and no changes were observed for auditees of the Big Six and for the groups of medium-sized and small audit firms investigated. These results, which pertain to a period when market concentration increased markedly (Beattie and Fearnley, 1994; Peel, 1997; Pong, 1999), offer some amelioration of the concerns of the purchasers of audit services that, in general, audit fees will rise in response to an increase in dominance by a few large firms.