Measured spectra ofθx,θy,θz, the derivatives of temperature in streamwise, lateral and vertical directions, respectively, indicate that the spectral densities ofθz andθy are nearly similar but significantly different from the spectral density ofθx. The high-frequency parts of the three spectra satisfy, in a qualitative sense, local isotropy requirements. In the high-frequency end of the inertial subrange, the relative behaviour of spectra ofθx,θy andθz is also consistent with local isotropy.