Broad agreement exists among both the investment banking and regulatory communities that the use of internal risk management models is an efficient means for calculating capital risk requirements. The determination of model parameters laid down by the Basle Committee on Banking Supervision as necessary for estimating and evaluating the capital adequacies, however, has received little academic scrutiny. We investigate a number of issues of statistical modeling in the context of determining market-based capital risk requirements. We highlight several potentially serious pitfalls in commonly applied methodologies and conclude that simple methods for calculating value at risk often provide superior performance to complex procedures. Our results thus have important implications for risk managers and market regulators.