A method using conductive heating is described for quickly obtaining and maintaining moderate temperatures in grain while minimising grain moisture loss. A model is developed to analyse insect mortality at a range of conditions on log-time logit and log-time probit scales. Values of LT 50, LT 99, and LT 99.9 are presented for adult and immature stages of Sitophilus oryzae in wheat from 42 to 48 degrees C at 12% m.c. and for immature stages of Rhyzopertha dominica in wheat from 45 to 53 degrees C at 9, 12 and 14% m.c. Data show that the heat tolerance of all life cycle stages for both species are different, with a degree of progressive change relative to each other as temperature changes, For R, dominica, the thermal tolerance of Life cycle stages also changes relatively with changes in grain moisture content, In general, all stages survive longer at a given temperature as grain moisture increases and the effect of moisture on survival increases as temperature decreases, Values for LT 99.9 for the most heat tolerant stage of R, dominica at 9% m.c. range from 78.22 to 2.49 h between 45 and 53 degrees C, At 12% m.c. they range from 96.81 to 3.36 h, and at 14% m.c. from 114 to 4.14 h, In general, at 12% m.c. the heat tolerance of S. oryzae is about 5 degrees C less than R. dominica with LT 99.9 ranging from 37.36 to 3.71 h between 42 and 48 degrees C, At this level of mortality, immature stage three is generally the most heat tolerant stage of R, dominica, whereas it is stage two for S, oryzae. The results are discussed in relation to practical applications of heat disinfestation and in terms of a general model of mortality, The results are also considered in the context of other available information on the heat treatment of both species. (C) 1998 Elsevier Science Ltd. All rights reserved.