The optical properties of pi-conjugated polymer films based on poly(p-phenylene vinylene) (PPV) units under a wet condition were studied. We succeeded in producing multimode laser emission under a wet condition from cylindrical microcavities with a polymer thin film fabricated onto the inner surface of an optical capillary tube, which was filled with cyclohexane. Furthermore, lasing spectral modulation was demonstrated with the polymer laser. We discuss the lasing spectral modulation by taking the change in refractive index into consideration. (C) 2010 Elsevier B.V. All rights reserved.