There has been a growing interest in urban design in the UK, and during the past decade it has become thoroughly embedded in government policy on town planning and urban regeneration. This has created a need for much greater clarity about what urban design is, and especially on how to implement it within the statutory framework of local planning policy. From the perspective of urban design practitioners, there has been a parallel desire to promote the idea of urban design, and to demonstrate how it can be implemented. This has generated a common interest in the publication of urban design guides, which can be used by relatively inexperienced practitioners to produce urban design frameworks and masterplans, and by local planning authorities considering planning applications or addressing problems of urban development or regeneration. To produce such a design guide, research evidence and theoretical knowledge of how people relate to public spaces in cities, and how their behaviour is influenced by design decisions, has to be ‘translated' into practical advice. The guides that have been produced so far show a remarkable uniformity in their recommendations, and appear to treat human behaviour in urban public space as a given body of knowledge, which is unproblematic and uncontested. This approach does not appear to be compatible with what is known about the complexity of human-environment behaviour, and the differences between competing theoretical perspectives, suggesting that the design guides may not be producing the most appropriate urban environments. The paper will begin with a brief summary of design guidance as a general body of literature, for example on housing and other specific building types, and specifically of guidance-oriented publications on urban design. This will touch on the work of Kevin Lynch, Donald Appleyard, Christopher Alexander, and others, and the more recent literature in the field of space syntax. The main body of the paper will focus on urban design guidance literature in the UK since 1990. Written from a design practitioner point of view, these guides appears to make a number of assertions about human behaviour in the built environment, both explicit and implicit. However, they also appear to be seriously lacking in theoretically grounded methodology, and may therefore be perpetuating half-truths and myths, or at least failing to appreciate the limitations of current knowledge. The paper will attempt to establish the nature and scope of the propositions about human-environment relations incorporated in design guides and their relation to theories of human environmental behaviour. The methodology of the study will be in two parts: (i) analysis of texts and interpretation of arguments, in order to identify claims and propositions about human-environment relations, for example that particular environmental design characteristics might or will influence or determine particular behavioural responses; and (ii) identification of sources, referenced and implied, and evaluation of the scientific basis for such claims about human-environment relations. In conclusion, it will consider if there is an adequate basis in theory and knowledge of human environmental behaviour to provide useful urban design guidance with sufficiently wide validity.