Hyperpolarization-activated, cyclic nucleotide-gated and cation-nonselective ion channels (I ( h ) channels, or HCN channels) are known to play important roles in mammals. Their physiological functions in invertebrate remain largely unclear. Here, we report our studies with I ( h ) channel in Drosophila melanogaster. Drosophila Ih channel mutants are found with several defects by behavioral analyses. Their lifespan is reduced, and their chemical sensitivity is shifted. In addition, their length of sleep at light-dark condition is mildly reduced. We generated transgenic flies of I ( h ) promoter-driven Gal4 and examined its expression pattern in both larvae and adult flies. Our results suggest that I ( h ) channel may play diverse roles in Drosophila and provide a basis to further expand our understanding of Drosophila Ih channel function in vivo.