Gender gaps in voter turnout are usually studied using opinion surveys rather than official census data. This is because administrative censuses usually do not disaggregate turnout according to voters' sex. Without this official information, much of the research on gender gaps in electoral turnout relies on survey respondents' self-reported behavior, either before or after an election. The decision to use survey data implies facing several potential drawbacks. Among them are the turnout overstatement bias and the attrition or nonresponse bias, both affecting the estimation of factors explaining turnout and any related statistical analysis. Furthermore, these biases may be correlated with covariates such as gender: men, more than women, may systematically overstate their electoral participation. We analyze turnout gender gaps in Chile, comparing national surveys with official administrative data, which in Chile are publicly available. Crucially, the latter includes the official record of sex, age, and the electoral behavior-whether the individual voted or not-for about 14 million registered individuals. Based on a series of statistical models, we find that analysis based on survey data is likely to rule out gender gaps in electoral participation. Carrying out the same exercises, but with official data, leads to the opposite conclusion, namely, that there is a sizable gender gap favoring women.