Owing to the different vapor pressures of zinc and selenium, the deviation from the stoichiometric compositions of the melt occurs during melt growth. In order to overcome this problem, we have adopted a closed double-crucible assembly consisting of an inner pBN crucible and an outer molybdenum capsule. To decrease the density of twins, an optimum temperature gradient at the growth interface of 30 K/cm and a growth rate of 3.6 mm/h have been determined. Using these growth conditions, we have grown successfully twin-free high-quality ZnSe single crystals with an EPD of 2.0 x 10(5) cm(-2) and an FWHM of 19 arcsec by the vertical Bridgman technique.