There have been numerous take-off accidents worldwide that were the result of a simple data calculation or entry error by the flight crew. This report documents 20 international and 11 Australian accidents and incidents (occurrences) identified between 1st January 1989 and 30th June 2009 where the calculation and entry of erroneous take-off performance parameters, such as aircraft weights and ‘V speeds’ were involved. Importantly, it provides an analysis of the safety factors that contributed to the international occurrences and suggests ways to prevent and detect such errors.