A novel ultraviolet-irradiation technique has been successfully developed to the synthesis of CdS nanocrystallites with different morphologies using poly(vinyl alcohol) (PVA) as protecting agent. The produced CdS samples may exhibit spherical, disk-like and wire-like morphologies by adjusting the concentrations of CdSO4.8/3H(2)O and thioacetamide (TAA). It is found that some nanotubes coexist in the sample of the US nanodisk, indicating it is possible to synthesize US nanotubes by the present approach. This method may extend to synthesize other metal sulfide nanocrystallites, nanowires, nanodisks, and even nanotubes.