OBJECTIVE: This study compared deaths from traffic accidents on Friday the 13th with those on other Fridays in a national population. METHOD: The author examined the daily deaths from traffic accidents by sex and age and the mean daily temperature in Finland, 1971-1997. Adjusted risk ratios for death on Friday the 13th versus other Fridays were obtained by negative binomial regression. RESULTS: In men, the adjusted risk ratio for dying on Friday the 13th, compared with other Fridays, was 1.02, but for women, it was 1.63. An estimated 38% of traffic deaths involving women on this day were attributable to Friday the 13th itself. CONCLUSIONS: Friday the 13th may be a dangerous day for women, largely because of anxiety from superstition. The risk of traffic deaths on this date could be reduced by one-third, although the absolute gain would remain very small: only one death per 5 million person-days.