APSL (Associação Portuguesa de Criadores do Cavalo Puro Sangue Lusitano) was founded by a group of members from the Associação Portuguesa de Criadores de Raças Selectas—a Portuguese association of breeders of selected breeds—who believed that the Lusitano breed required an exclusive studbook. This studbook was established in 1967.

The studbook was officially recognized by the Portuguese government in 1989 through the Ministry of Agriculture, which took on the responsibility for managing the Lusitano studbook.

The purpose of APSL is to defend and promote the Lusitano horse and to maintain the closed studbook. This is to ensure the breed's genetic purity and to help improve its development.

The maintenance and improvement of the breeding program were results of the Lusitano's evolution. Originally used as a war horse and for agricultural work, the breed gained recognition in recreational and sports activities, such as bullfighting, leading to its current status.

APSL has about 400 active members and serves as an umbrella organization for breeders. Members benefit from the various services APSL offers, including ownership transfers, issuance of the studbook (the "blue book"), and more. (For more information about APSL, click here.)