Intermittent hypoxia (IH) with repeated episodes of hypoxia-normoxia cycle have been shown to exert preconditioning-like cardioprotective effects. To understand the mechanism of these events, we investigated the changes in cardiac gene expression in response to acute IH. Mice were subjected to 5 cycles of 2-min 10% O₂ + 2-min 21% O₂. RNA was isolated and gene array analysis was performed. Results show that the expression of anti-apoptotic genes such as Bcl-2 and Bcl-x_L were increased after acute IH. GATA-4 regulates transcription of these genes, and consistently GATA-4 activity was increased by acute IH. Although the phosphorylation of GATA-4 has been shown to regulate its activity, no changes in GATA-4 phosphorylation status by acute IH were noted. Gene transcription of gata4 was increased by acute IH, and this might be responsible for the enhanced GATA activity. To understand the mechanism of acute IH activation of gata4 gene transcription, we identified a promoter region of the mouse gata4 gene that is 1,000 bp immediately upstream from the transcriptional start site. In cardiac muscle cells, truncation of 1,000 bp to 250 bp did not alter the transcriptional activity, suggesting that the proximal 250 bp region contains important transcriptional regulatory sites. We further found that acute IH activates factors, which bind to the proximal 100 bp region. Thus, acute IH activates not yet identified factors, which bind to the proximal 100 bp region of the gata4 promoter, and in turn increases gata4 gene transcription, leading to enhanced expression of Bcl-2 and Bcl-x_L.