We examine the effect of consumer and market factors on the trial probability of new consumer packaged goods. We distinguish between three sources of variation in consumer trial probability: (1) within new products, across consumers; (2) within new products, over time; and (3) across new products. Hypotheses are developed for the different variables concerning their likely effect on trial probability. The hypotheses are tested on weekly household-panel scanner data on the occurrence and timing of first purchases for 239 new consumer packaged goods over a 52-week period after introduction for a sample of over 3,500 consumers. We combine these household panel purchase data with consumer questionnaire data, retail scanner data, data on advertising expenditure, and expert ratings. We find support for most hypotheses. One of our main findings is that the effects of the consumers' personal makeup on the probability that they will try the new product are systematically moderated by elements of the marketing strategy associated with the new product and by category characteristics. The extensive data set provides a strong context for the generalizability of the findings.