Resumen
Accuracy of quantity surveyors? preliminary cost estimates was evaluated through a questionnaire surveyadministered on quantity surveying firms in Nigeria. A total of 24 quantity surveying firms were surveyed and data on 40completed and on-going projects collected to quantitatively measure the degree of accuracy of quantity surveyors?preliminary cost estimates. The survey also evaluated preliminary cost estimating procedures employed generally. Withinthe limitation of the sample data analysed, it was concluded that quantity surveyors? preliminary cost estimates in Nigeriawere not significantly biased. However, the consistency of the estimates was found to be unsatisfactory and as such, anissue that needs to be addressed. Using analysis of variance (ANOVA), the paper also concluded that estimating accuracyimproved with increasing contract size. However, for very large contracts, this was found to be contrary; the reasonsadduced being time lag between preliminary cost estimate and invitation of tenders and political factors that are commonwith such projects.