To provide information required in the preparation of the Greater London Development Plan. Estimates of the future population of London were to be based on the stock of dwellings that would exist in London. It was therefore necessary to know more about the condition and useful life of existing housing. At the same time, if occupancy rates were to be projected accurately, more needed to be known about the pressure for homes from <i>hidden</i> households (those living as part of another household because they cannot find separate accomodation). Variables Just over one hundred thousand properties were selected for inspection and the information listed below was collected. This was done in such a way that analysis could be made in terms of rateable units, of census dwellings and in terms of a reasonable unit of accomodation, referred to as a dwelling unit. The information covered: a) Useful life b) Condition of dwelling, under the headings: 'structure' and `maintenance' c) Type of dwelling d) When built e) Tenure f) Number of households g) Number of rooms and facilities available h) Whether likely to be demolished for planning reasons in the next ten years i) Whether suitable for improvement or conversion j) Cost of improvements or conversion k) Number of parking spaces.