The isolation and characterization of a restriction endonuclease from Bacillus cereus IOC 243 are described. The enzyme recognizes the palindromic sequence 5’-G(met-A,A)TC-3’ as determined by PEI chromatography of pancreatic DNase, snake venom phosphodiesterase digestion products of labelled fragments, analysis of restriction digests from normal and N6-methyladenine-free DNA and direct sequence analysis of cloned fragments. The staggered cleavage products with 5 ‘-terminal pGATC extensions are efficiently labelled with polynucleotide kinase and are easily cloned into BamHI sites. The enzyme, denoted Bce243, is thus an isoschizomer of SaufAl. Its use and potential advantages in substituting Sau3AI are discussed.