Using measurements of all three components of the temperature dissipation &khgr; in a laboratory boundary layer, the measured probability densityp(&khgr;r) of &khgr;r, or &khgr; averaged over a distancer, is found to be closely log‐normal over a significant range ofr. The variance &sgr;2of ln&khgr;rfollows the relation &sgr;2=A+&mgr;ln(L/r), with &mgr;=0.35, whereLis an integral scale of turbulence. High order moments, up to order 5, of &khgr;rshow a power‐law variation withr/L. With increasing order of the moment, the power‐law exponents become increasingly smaller than the corresponding values implied by assumed log‐normality ofp(&khgr;r) but are consistent with the bounds given by Novikov’s theory. It is suggested that the observed close agreement with log‐normality ofp(&khgr;r) may be misleading when sufficiently high order moments of &khgr;rare considered.