Abstract: Melbourne’s open space system spans property boundaries over public and private lands, and provides key social and ecological services. With significant population growth predicted over the next 50 years, high levels of infill housing will be required. Increasing house sizes and infill development practices are directly modifying the quantity and quality of private open space in inner and middle belt suburbs. The distribution of public open space in Melbourne is uneven, with most inner municipalities, and 6 of 13 middle municipalities, having a shortage of public open space per capita. Focusing on public and private open space at ground level, this paper aims to assess how residential infill developments are impacting on open space availability. The method uses rates of detached dwellings and lot size to approximate private open space availability, and rates of recent detached and higher density dwelling construction to indicate infill development in each municipality across metropolitan Melbourne. These rates provide sufficient indicators to assess open space in fully developed inner and middle municipalities with predominantly suburban forms - but not areas with large amounts of high density or greenfields development. The results suggest that infill pressures and open space availability varies significantly throughout Melbourne. Current open space policy mechanisms have not been developed with the capacity to regulate infill development in a way which would allow open space across land uses to provide continuing health, recreational and environmental services to support the growing population