It is well known that the mortality rate of patients admitted to hospitals over the weekend is higher than that for patients admitted during the week. Whether, or to what extent, this ‘weekend effect’ is caused by case-mix factors vs. care quality factors is one of the big unknowns. This is being investigated by a CLAHRC WM-associated HS&DR grant led by Prof Julian Bion with economic support from Sam Watson, the CLAHRC WM Director and Jo Lord. We were thus provoked by a recent article by Meacock at al investigating the health economics of providing increased consultant support over the weekend. The health gain is calculated on the basis of avoiding all of the excess in deaths and this is offset against the cost of providing a seven-day service. Based on their calculation, the authors find that even if the weekend effect could be eliminated, it would not justify the cost of the service at the NICE willingness-to-pay threshold. In other words, the opportunity cost is such that it would be better to leave the money doing what it is currently doing (if no new money), or to allocate it elsewhere (if new money). However, preventable deaths are merely the top of the adverse event severity pyramid and if the adverse events come down roughly in proportion to deaths, then the gains are much greater and the cost much lower than estimated in the paper. CLAHRC WM collaborators have produced a model to estimate the costs and benefits of reducing adverse events.