Thermal conductivity and thermal expansion for Ir3X (X = Ti, Zr, Hf, V, Nb, Ta) were measured in the temperature range between 300 and 1100 K. The thermal conductivities of Ir3X are distributed in the range from 41 to 99 W m(-1) K-1 at 300 K, while the difference of thermal conductivities becomes less emphasized at higher temperatures. The coefficients of thermal expansion (CTEs) of Ir3X are insensitive to temperature, which fall around 8 x 10(-6) K-1 at 800 K. (C) 2002 Elsevier Science B.V. All rights reserved.