This study investigates how the quality of stocks owned by mutual funds affects the performance of those funds during 2000-2009. The quality of a stock is positively related to its size, while quality is inversely related to volatility. Evidently, stocks in the lowest quality decile perform particularly poorly amidst volatile market conditions with a mean monthly Daniel, Grinblatt, Titman and Wermers (DGTW) alpha 1.93% [25.73% per annum (pa)] less than high-quality stocks. Furthermore, funds which hold the lowest quality stocks exhibit substantial underperformance, particularly during market downturns, with funds in the lowest decile of quality incurring a mean monthly DGTW alpha 0.96% (12.14% pa) lower than their higher quality counterparts. Interestingly, we discover a trend to funds investing in higher quality stocks over time.