Religious conversion is often an overwhelming experience. Although self-reports by some converts about life before and after conversion often contain vivid descriptions of the type and extent of changes, few rigorous empirical studies have documented them. This 3-year longitudinal prospective study aimed to understand the precursors of conversion, and whether this event would result in psychological changes. A logistic regression on 455 non-Christian Chinese (of whom 46 later became Christian converts) showed that neither baseline personality, personal values, social axioms, nor psychological symptoms predicted whether one would be converted during the next three years. However, people who thought that there is one and only one true religion were more likely than others to be converted. We further formed a matched sample of 92 individuals who had been Christians throughout the study, and a matched sample of 92 nonbelievers who remained so throughout the study. Comparison between measures taken at the baseline and end of the study period showed that converted people were transformed not in personality but in symptoms of stress and anxiety, as well as several personal values.