Building on an earlier Trends and Issues paper, "The Psychology of Fraud" (No. 199), this paper identifies warning signals for fraud, and proposes some preventive or pre- emptive action. Four fraud types are examined: entrepreneurial fraud; client or employee fraud; direct interpersonal fraud (face-to-face); and indirect mass fraud. Examples of each of these are evident in our daily lives and there are often warning signals. Not all of these "warning signals" are necessarily precursors to fraud, but it should be noted that the most productive investment in fraud control is likely to involve strategies which reduce opportunity and enhance guardianship. The setting or context in which fraud may occur can be more or less conducive to offending. This paper aims to enhance our understanding of the situational elements of fraud risk, to permit the design of effective fraud control systems.