Direct numerical simulations of dilute two-phase flows are conducted to study the decay of the fluid and particle temperatures in isotropic turbulence. Both one-way and two-way couplings between phases are considered. The effects of the particle response time (tau(p)), the Prandtl number (Pr), the ratio of specific heats (alpha), and the mass loading ratio (phi(m)) on the carrier fluid and particle temperature statistics are studied. The results indicate that the variance of the fluid and particle temperatures, the dissipation rate of the fluid temperature and the high wavenumber values of the fluid temperature spectrum are increased as the magnitudes of phi(m) and/or alpha Pr increase. The decay rate of the fluid and particle temperature variances an similar when the values of alpha Pr are small. For large alpha Pr values, the variance of the particle temperature is higher than that of the fluid and is strongly dependent on the initial conditions. The Lagrangian auto-correlation coefficient of the particle temperature (R-T(p)) also behaves differently for different magnitudes of alpha and Pr. For small values of alpha, R-T(p) decreases as the magnitude of particle response time increases. For large values of alpha, R-T(p) increases with increasing tau(p). (C) 2000 Elsevier Science Ltd. All rights reserved.