This report assesses changes among monthly gamblers in online panel surveys in Massachusetts in gambling attitudes, gambling participation and problem gambling prevalence from 2014 to 2023. Results refer only to panel members and not to the population of Massachusetts. Among monthly gamblers, attitudes toward gambling have grown more negative. Between 2022 and 2023, there were increases in gambling participation among monthly gamblers, which suggests that the lingering impact of COVID-19 on gambling behavior among monthly gamblers may be diminishing. There was an increase in sports betting participation among monthly gamblers, but there does not yet appear to be substantial recapture of sports betting revenues among monthly gamblers in the wake of legalization despite a reduction in the proportion of sports bettors among monthly gamblers who only gamble on sports illegally. Finally, among monthly gamblers, there may have been an increase in people experiencing gambling harms and gambling problems between 2014 and 2023.