The problem of the proliferation of the number of aid donors and aid channels continues to worsen. It is widely and plausibly believed that this significantly; reduces the value of aid by increasing direct and indirect transactions costs. We contribute to the existing literature by: (a) categorising the apparent adverse effects of proliferation; (b) producing a reliable and fair indicator of the relative degree to which the main bilateral donors proliferate or concentrate their aid; (c) giving some explanation of why some donors proliferate more than others; (d) constructing a reliable measure of the extent to to which recipients suffer from the problem of fragmentation in the sources of their aid; and (e) demonstrating that the worst proliferators among the aid donors are especially likely); to be suppliers of aid to recipients suffering most from fragmentation. There are significant implications for aid policy.