Modeling capabilities for longitudinal data have progressed considerably, but questions remain on the extent to which method bias may negatively affect the validity of longitudinal survey data. The current study addresses the stability of individual response styles. We set up a longitudinal data collection in which the same respondents filled out 2 online questionnaires with nonoverlapping sets of heterogeneous items. Between data collections, there was a 1-year time gap. We simultaneously modeled 4 response styles that capture the major directional biases in questionnaire responses: acquiescence, disacquiescence, midpoint, and extreme response style. Drawing from latent state-trait theory, we specified a 2nd-order factor model with time-invariant and time-specific response style factors and a specifically designed covariance structure for the residual terms. The results indicate that response styles have an important stable component, a small part of which can be explained by demographics. The meaning and implications of these findings are discussed.