This study identifies some alternative conceptions of chemical kinetics held by secondary school and undergraduate students (N = 191) in Turkey. Undergraduate students who participated are studying to become chemistry teachers when they graduate. Students' conceptions about chemical kinetics were elicited through a series of written tasks and individual interviews. Several alternative conceptions exhibited by secondary school students persisted among undergraduates, indicating the persistence of such alternative conceptions. The results suggest that students' lack of understanding in thermodynamics and chemical equilibrium significantly influences their conceptions about chemical kinetics. Implications for instructional approaches particular to chemical kinetics are discussed. (Contains 1 table and 2 figures.)