Based on our previous work on the standard measure of risk, this paper presents twoclasses of measures for perceived risk by considering a two-dimensional structure, the mean of alottery and its standard risk. One of the classes of our risk measures presumes that there is no riskif and only if there is no uncertainty involved and the other allows that different degeneratelotteries may be evaluated with different values of "risk". The former has more prescriptiveappeal in risky decision making and the later has more descriptive power for subjective riskjudgments. Our risk measures can also take into account the asymmetric effects of losses andgains on perceived risk. It is demonstrated that our perceived risk models unify a large body ofempirical evidence regarding risk judgments and can be incorporated into preference models (i.e., based on risk-value tradeoffs) in a clear fashion.