Gross Domestic Product of any country often influence economic decisions by policy makers, market participants and econometricians on policy recommendations, evaluation and forecasting. However these decisions are often based on preliminary data announcements by statistical agencies. It is therefore important to ensure that the preliminary GDP announcements are efficient and can be relied on. This paper focuses on South Africa's preliminary announcements of quarterly GDP estimates by examining the relationship between the preliminary data and revised data using Ordinary Least Squares estimation technique. The results of this research suggest that the preliminary estimates of GDP, GDE, final consumption Expenditure by Households and by General Government for the period 1999Q1 to 2013Q4 are not efficient.