Local bending propensity and curvature of DNA can be characterized using a vector description of DNA bendability, based on a set of parameters derived from deoxyribonuclease I (DNase I) cleavage experiments. Two characteristics-arithmetic and vector averages of bendability-were successfully used to predict experimentally known bendable, rigid and curved segments in DNA. A characteristic distribution of bendability is conserved in evolutionarily related kinetoplast sequences. An analysis of the M. genitalium and H. influenzae genomes as well as fragments of human and yeast genomes shows, on the other hand, that highly curved segments--similar to artificially designed curved oligonucleotides--are extremely rare in natural DNA.