DNases A₁ and A₂ have been purified to homogeneity from the hepatopancreas of Achatina fulica by a series of steps: acetate buffer extraction, ammonium sulfate precipitation and column chromatography on hydroxylapatite, phosphocellulose, Blue-Sepharose, and poly(A)-Sepharose. The purified enzymes are free of acidic phosphomonoesterase, phosphodiesterase, and RNase activities. They are slightly acidic glycoproteins with identical isoelectric point (6.90).On 0.1% SDS gel electrophoresis, DNase A had a molecular weight of 30,000 when dissolved in 1% SDS, but it had molecular weights of 17,500, 8,000, and 4,800 when dissolved in 1% SDS and 1% 2-mercaptoethanol. This was evidence that the enzyme consists of three different subunits joined by interchain disulfide bonds. DNases A₁ and A₂ are endonucleases working at acidic pH (3.5–6.0) and do not require divalent cations for their activities. The enzymes degrade poly(dA) 5 times faster and poly(dT) 3 times faster than heat-denatured DNA under optimal conditions but do not appreciably digest poly(dG) and poly(dC). We developed an analytical procedure for oligodeoxynucleotides by high-performance liquid chromatography. The phosphomonoester end group and the mode of degradation were examined by the method. The termini produced by the enzymes have 3'-phosphoryl and 5'-hydroxy end groups. The products of exhaustive hydrolysis contain di-, tri-, tetra-, and pentanucleotides and mononucleotide was barely detected. The hydrolyzing activities of DNases A₁ and A₂ are stimulated by polyamines such as spermine, spermidine, and putrescine, but are inhibited by synthetic polynucleotides and various drugs. Adenosine deaminase highly active on oligoadenylic acids was found in a crude DNase A fraction. The enzyme preparation has higher activity on 3'-adenylic acid than on 5'-adenylic acid. The first adenosine residue of oligoadenylic acids was deaminated considerably more rapidly than the second or succeeding ones.