This paper contributes to strengthening this evidence base providing better guidance to donors around how they can best facilitate private sector contributions to sustainable development outcomes, as envisaged in the Addis Ababa Action Agenda. It does this by illustrating firstly how donor support to the enabling environment for private sector development fits alongside, and underpins, other catalytic aid approaches. And secondly by highlighting how available data can (or, indeed, struggles to) inform decisions to maximise the impact of donors' catalytic interventions in different groups of developing countries.