Some effects of low temperatures on diapause and non-diapause larvae of the pine caterpillar, Dendrolimus tabulaeformis Tsai et Liu (Lepidoptera: Lasiocampidae), were investigated in laboratory experiments. The results indicated that diapause larvae had higher survival rates than non-diapause larvae at earlier stages of exposure to the low temperatures (-10, -17 and -21 degrees C). In general, the larvae lives were shorter when they were exposed to the lower temperatures. Exposure to chilling at 0 degrees C (cold pulse) in advance increased the survival rate of larvae when they were exposed to -10 degrees C, and the survival rate increased with the length of cold pulse (doubled at 50 min). No larvae could survive after the 50th day of daily exposure to -10 degrees C for 1 h followed by exposure to 27 +/- 1 degrees C for 23 h. The water contents of diapause and non-diapause larvae differed significantly, and the super-cooling points (SCPs) of non-diapause larvae were significantly higher than those of diapause larvae.