Aspects of residential apartment amenity have acquired a new importance due to the influence of State Environmental Planning Policy 65 - Design of Residential Flat Buildings. This paper raises the issue that failure to achieve prescribed quantitative measures often does not mean that proposed designs will fail to comply with the Policy’s more complex performance criteria. For the sake of brevity, the discussion focuses only on natural ventilation. Whilst SEPP 65, Principle 7 - Amenity - refers to “natural ventilation”, supporting documents specify or describe “cross ventilation”. The paper explores concepts of ventilation, describes the necessary conditions for natural ventilation to be effective, and considers the need for, and advantage of, cross ventilation. The paper was presented at a NEERG Seminar for professionals and local government personnel involved in development approvals of residential construction in NSW, Australia.