The necessary and sufficient as well as meaningfulness conditions that elicited information on conditional and joint probabilities must satisfy are evaluated against actual assessments empirically. A high frequency of violation of these conditions was observed in assessing both conditional and joint probabilities. The consistency of the assessments is affected by factors such as the causal/diagnostic and positive/negative relationship of the events. Use of a joint probability table as a judgemental aid can significantly reduce the number of inconsistent conditional as well as joint probability assessments. The implications of assessing conditional versus joint event probabilities to obtain consistent and meaningful probabilistic input for forecasting ad decision-making are discussed.