When information is sold, there is often a reliability problem since anyone can claim to have superior knowledge. Optimal strategies which allow a seller to establish that he is informed are considered in a standard one-period, two-asset model. When risk aversion is unobservable, an information market is viable and both the seller and the buyers are better off participating. However, the seller cannot obtain the full value of his information because of the reliability problem. This provides an opportunity for intermediation since an intermediary may be able to capture some of the remaining value.