We introduce a class of multifractal processes, referred to as multifractal
random walks (MRWs). To our knowledge, it is the first multifractal proces
s with continuous dilation invariance properties and stationary increments.
MRWs are very attractive alternative processes to classical cascadelike mu
ltifractal models since they do not involve any particular scale ratio. The
MRWs are indexed by four parameters that are shown to control in a very di
rect way the multifractal spectrum and the correlation structure of the inc
rements. We briefly explain how, in the same way, one can build stationary
multifractal processes or positive random measures.