Actinobacillus pleuropneumoniae (App.) is the major causative agent of swine pleuropneumonia, a highly contagious respiratory disease. App. can be classified as biotype I (NAD-dependent) of biotype II (NAD-independent). Type I consisted of 14 serotypes (1-13 and 1.5) and type II has 7 serotypes (2, 4, 7, 9,11,13 and 14). Several virulence factors are known for App. such as cytotoxins, capsular polysaccharides and lipopolysaccharides. In this review, the past and current knowledge on biotypes, serotypes, virulence factors of App. as well as laboratory diagnosis and vaccines is summarized. This review also includes some data on App. in Vietnam.