We have been able to observe the surface-enhanced Raman scattering (SERS) from 4-mercaptopyridine (4-Mpy) molecules adsorbed on ZnO nanocrystals, which display 103 enhancement factors (EFs). An excitation wavelength-dependent behavior is clearly observed. Another molecule BVPP is also observed to have surface-enhanced Raman signals. The chemical enhancement is most likely responsible for the observed enhancement, since plasmon resonances are ruled out. The research is important not only for a better understanding of the SERS mechanism, but also for extension of the application of Raman spectroscopy to a variety of adsorption problems on a semiconductor surface. Copyright © 2009 John Wiley & Sons, Ltd.