Existing approaches investigating access to primary health care tend to use relatively crude measures that compare supply to demand ratios for administrative units or use GIS to calculate straight-line or network distances to the nearest facility. The latter however largely assume access is via private modes of transport. The aim of this paper is to investigate the impact of different modes of travel (car versus bus) on associations between different measures of General Practitioner (GP) supply and area level deprivation and the percentage of elderly patients. Multivariate regression techniques are employed to examine relationships between demand and potential accessibility to GP services for different modes of travel for a study area in South Wales, UK. Accessibility measures are calculated using ‘traditional’ GIS-based approaches and Enhanced Two-Step Floating Catchment Area (E2SFCA) techniques. Findings suggest that, whilst the direction and strength of the association between deprivation and accessibility measures varies by mode of travel, the main differences are actually across measures of accessibility. This has important implications for studies of potential inequalities in health service accessibility and suggests there is a need to develop consistent measures of accessibility if we are to truly understand the relationship between demand and supply. Such studies should ideally incorporate the availability of alternative modes of transport particularly in areas where there are vulnerable groups such as the elderly who are typically more dependent on public transportation to access health care services.