Effects of rating scale forms on cross-sectional reliability and measurement equivalence were investigated. A randomized experimental design was implemented, varying category labels and number of categories. The participants were 800 students at two German universities. In contrast to previous research, reliability assessment method was used, which relies on the congeneric measurement model. The experimental manipulation had differential effects on the reliability scores and measurement equivalence. Attitude strength seems to be a relevant moderator variable, which influences measurement equivalence. Overall, the results show that measurement quality is influenced by rating scale forms. Results are discussed in terms of their implications for latent variables measurement.