Abstract: Thirteen hsp70 genes with complete conserved domains were identified in Tetrahymena thermophila, and expression of five similar and non-intron hsp70 genes were analyzed. Under heat shock conditions of 37, 39 and 41ºC, hsp70-2 mRNA had the highest relative expression level, suggesting it is closely related to heat shock. The basal level of constitutive T. thermophilahsp70-4 gene was high during 20 physiological/developmental stages of growth, starvation and conjugation, and it changed little upon exposure to heat shock: evidence that hsp70-4 is an hsc70 gene. The hsp70-4 cDNA is 2 208 bp long, and contains an open reading frame of 1 959 bp encoding 635 amino acids. Microarray data indicated that T. thermophilahsp70-3 gene probably participated in early starvation (0–12 h) stress and late conjugation (6–10 h) events, such as new macronuclear and micronuclear anlagen formation and old macronuclear elimination. However, hsp70-5 gene possibly participates in late starvation (12–15 h) stress and early conjugation (0–6 h) events such as micronuclear meiosis, micronuclear exchange and pronuclear fusion. Blast2GO indicated that they participated in dissimilar biological processes, suggesting hsp70-3 and hsp70-5 perform different functions.