The pure POPOP dye vapor is excited in a transverse geometry by an N2laser and the output power of the laser is measured as a function of temperature and intensity of the exciting laser. The threshold temperature is about 310°C and the maximum output power is obtained at around 390°C. The threshold intensity of the exciting laser is about 0.3 MW/cm2and the output power is almost linearly dependent on the intensity as far as experimentally observed. The shift of the oscillation wavelength is observed with increasing temperature and the central wavelength of the broad-band laser can be tuned from 385 to 402 nm by the selection of the vapor density. Theoretical results calculated from rate equations which are dependent on time and space qualitatively agree with these experimental results. The effect of reflectance of the cavity on the output power is also discussed.