The monks successfully developed this breeding program, which gained widespread recognition throughout Europe in the 18th century.

Morphologically, the Carthusian horse is characterized by a lighter body and a straighter head profile compared to other PRE lines, often exhibiting bony protuberances.

Carthusian breeding is primarily concentrated in its region of origin, Andalusia, particularly around Jerez de la Frontera, Badajoz and Córdoba.

[9] There was a spiritual dimension to this breeding, as evidenced by an account of the perception of God's face in a horse's eye.

The Carthusian bloodline was solidified in the early 18th century when brothers Andrés and Diego Zamora acquired a stallion named El Soldado, along with two mares descended from horses purchased by the King of Spain, which had been placed at Aranjuez, one of Spain's oldest stud farms.

[5][4] One of El Soldado's descendants, a dark gray colt named Esclavo, became the founding sire of the lineage.

[5][13] Esclavo was sold to Don Pedro Picado in Portugal,[14] but a group of mares he had sired were given to Carthusian monks to settle a debt, around 1736.

[5] Over the next century, the Carthusian monks fiercely protected this lineage, resisting royal orders to cross their horses with Neapolitan and Central European breeds, although they did introduce Arabian and Barb bloodlines to improve their stock.

[13] In 1835, the convent's stud farm was dissolved, and management of the horses was transferred to the Spanish state and select private breeders.

[12] Overall, the Carthusian horse is lighter and more slender compared to other PREs, characterized by its elegance, strength, and well-conformed body.

[19] The head is relatively small, light, and well-shaped, often described as rectilinear or slightly convex,[2][12][21] and considered more beautiful and noble than in other PREs.

[12] A rare feature is the presence of two small bumps on the bridge of the nose,[9][22] referred to as "horns", which are calcium deposits located beneath the ears and thought to be inherited from Asian ancestors; however, this characteristic is not a criterion for lineage recognition.

[12] The rump is round[12] or sloping,[5] with the tail set fairly high, carried raised in movement.

[6] Carthusian horses are predominantly gray,[19][20][9][12] a trend attributed to the use of two breeding stocks with this coat color in the first half of the 20th century.

[29] The Carthusian, along with the Moyle and the Chinese "dragon horse", is notable for featuring bony protuberances on the muzzle.

[30] Thomas Terry, a member of the Marbella Club and a wine and spirits merchant, is also a breeder of Carthusian horses.