All three components of the dissipation rate of the fluctuating temperature &Vthgr; are measured simultaneously in the inner region of a fully developed turbulent boundary layer at a moderate Reynolds number. Measurements are made with a probe of four cold wires consisting of two closely spaced parallel vertical wires mounted a small distance upstream of two closely spaced parallel horizontal wires. In the inner region of the layer, local isotropy is not closely approximated (∂&Vthgr;/∂z)2⟩ (∂&Vthgr;/∂y)2⟩ (∂&Vthgr;/∂x)2. The spectral density of the sum &khgr;[= (∂&Vthgr;/∂x)2+(∂&Vthgr;/∂y)2+ (∂&Vthgr;/∂z)2] is similar in shape to that of (∂&Vthgr;/∂y)2or (∂&Vthgr;/∂z)2but not as rich in high frequency content as that of (∂&Vthgr;/∂x)2. The probability density of &khgr; has a lower skewness and flatness factor and is more closely log‐normal than those of the individual components. This is true regardless of whether &khgr; and its components are unaveraged or locally averaged over a linear dimensionr. When averaging is applied, departures from log‐normality are diminished but do not disappear entirely. The variance &sgr;2of the logarithm of the locally averaged &khgr; is proportional to lnrover a wide range ofr(rmax/rmin≃30), in contrast to the individual components where this ratio may be as small as 2. The value of the Kolmogoroff constant &mgr;&Vthgr;determined from the slope of &sgr; vs lnris about 0.35. This is consistent with the slope of the spectral density of &khgr; and is also in agreement with previous best estimates of &mgr;&Vthgr;(and &mgr;) obtained at high Reynolds numbers.