The longitudinal d(33) piezoelectric coefficient was studied in rhombohedral Pb(Zr0.6Ti0.4)O-3 thin films with (111), (100), and "random" orientation. The largest d(33) was found in (100)-oriented films and the smallest along the polarization direction in (111)-oriented films. These results are in a good qualitative agreement with recent theoretical predictions [Du, Zheng, Belegundu, and Uchino, Appl. Phys. Lett. 72, 2421 (1998)]. The field dependence of d(33) was also investigated as a function of crystallographic orientation of the films. It was found that (100)-oriented films with the highest piezoelectric coefficient exhibit the weakest nonlinearity. Observed variation in the piezoelectric nonlinearity with film orientation can be fully explained by taking into account domain-wall contributions, which are dependent on film orientation. (C) 2000 American Institute of Physics. [S0003-6951(00)02912-0].