We have prepared high purity ZnSe single crystals with donor concentrations less than 1015/cm3 and characterized the doped and undoped ZnSe single crystals using photoluminescence and cyclotron resonance techniques. Photoluminescence and photoluminescence excitation spectra on the purest crystal reveal (1) that a Zn-dip treatment increases the free exciton life time, (2) that the free excitons recombine on the lower excitonic polariton branch, (3) that the intensities of I3 become larger than those of I2, and (4) that each I3 line has excited states, which are rather more complicated than those of the I2 lines. We have observed for the first time cyclotron resonance absorption of photoexcited electrons and holes. This means that the grown crystals are not only of high purity but also of high quality. Isotropic effective masses (m∗e = 0.145m0 and m∗h = 1.04m0) and cyclotron mobilities at 4.2 K (μe = 470,000 cm2/V·s and μh = 210,000 cm2/V·s) have been obtained. Doping experiments with In and Cu reveal that the difficulties of preparing low resistivity p-type crystals, such as self-compensation and the amphoteric behavior of dopants, can be solved by heat treatments after doping.