Researchers often assume that respondent burden influences survey participation propensity and that interview length is a good indicator of burden. However, there is little evidence of the effect of interview length on subsequent participation propensity, particularly for face-to-face surveys. In a randomised experiment, respondents experienced interviews of different lengths at wave 1 of a panel survey. Subsequently, they were asked to complete a self-completion questionnaire and to take part in further waves of the survey. Response rates to these subsequent tasks are compared between those administered the shorter and longer versions of the wave 1 interview. No evidence is found that wave 1 interview length affects subsequent participation propensity.