This research examines description in the office sector with particular reference to the city of Kuala Lumpur. Depreciation is typically considered implicitly in appraisal models. Furthermore, from the early 1990 until 1996, the impact of depreciation in the office market was largely hidden by high nominal growth in rents and capital values due to high inflation and high real growth. Improper analysis of depreciation may have potentially damaged property values and consequently mispriced the city's market. It is, therefore, important to analyse depreciation comprehensively to assess proper prices in the city's office market. This study is designed to achieve a better understanding of depreciation. The research proposes a statistical approach for modelling the impact of depreciation on the City of Kuala Lumpur offices and considers three major causes of depreciation; physical deterioration, building obsolescence and site obsolescence. Forty-nine offices which are located in the three commercial areas are selected. Data on property characteristics, tenure and values were analysed. Principal Component Analysis eliminates the problem of 'multicollinearity' which exists in the models with original variables, and summarises independent variables into a number of orthogonal factors which represent three sources of depreciation. An analysis of rental depreciation indicates that a combination of the three sources of depreciation is a better explanation of depreciation than 'age' alone. It shows that, despite the common suggestion that the level of depreciation changes markedly with building age, there is little evidence to conclude that these are strongly correlated. The findings of the analysis indicate that the relative rate of depreciation for offices in the City of Kuala Lumpur is dependent on changes to the functional specifications of the buildings. The faster the changes, the quicker the rate of depreciation. Finally, site obsolescence is shown to be less significant than functional specifications, especially in yield depreciation, in the case study area.