The nine ryu (traditions or schools) are what Bujinkan Budo Taijutsu is based on.

Three of the ryu are specialized as Ninjutsu schools, where some are more specialized in espionage, information gathering, geometry, tactics etc. rather than combative techniques.

The other six ryu are more specialized in combative techniques (although most of them have Ninpo elements in them). Some with many weapons and others more specialized in unarmed combat.

Today the training is broadened on the combative techniques rather than Ninjutsu. This is why Hatsumi Sensei prefers to call our art Budo Taijutsu.

The following is a brief introduction to each of the nine schools

Togakure-ryu Ninpo Happo Biken was founded in the late 1100's by Daisuke Nishina. The second oldest Ryu in Masaaki Hatsumi's Bujinkan Budo Taijutsu system. This school is most famous in Bujinkan for the different Ninjutsu weapons as the Shuko, Shinodake, Shuriken, etc.

Gyokko-ryu Kosshijutsu Happo Biken was founded in the mid 1100's by Tozawa Hakuunsai. The oldest Ryu in Masaaki Hatsumi's Bujinkan Budo Taijutsu system. Most famous for the Kihon Happo, Sanshin no kata, and Muto Taihenjutsu which are considered as the basics in the Bujinkan system.

Kukishin-ryu Taijutsu Happo Biken was founded in the mid 1300 by Izumo Kanja Yoshitero. Most famous in Bujinkan for the many different weapon techniques.

Shindenfudo-ryu Dakentaijutsu Happo Biken was founded in the beginning of 1100 by Izumo Kaja Yoshitero. Most famous in Bujinkan for the rough Dakentaijutsu techniques. This school was the theme of 1998 and was taught at the Italian, Sweden, US and Japan Taikai.

Gyokushin-ryu Ninpo Happo Biken was founded in the mid 1500 by Sasaki Goemon Teruyoshi. Very little of this school have been taught to the western world. It is believed that this school was more into information gathering and planning than actual combat.

Koto-ryu Koppojutsu Happo Biken was founded in the mid 1500 by Sakagami Taro Kunishige. Most famous in Bujinkan for the Koppojutsu (bone breaking techniques), and unusual Biken (sword) style of fighting.

Gikan-ryu Koppo Taijutsu Happo Biken was founded in the mid 1500 by Uryu Hangan Gikanbo. Most famous in Bujinkan for the difficult and odd Kamae in it's Taijutsu. This school is also specialized in Koppojutsu.

Takagiyoshin-ryu Jutaijutsu Happo Biken was founded in the beginning of 1600 by Takagi Oriuemon Shigenobu. Most famous in Bujinkan as a "Bodyguard School" fast and effective Jujitsu techniques, and Daishosabaki (Jujitsu while wearing both swords in the belt).

Kumogakure-ryu Ninpo Happo Biken was founded in the mid 1500 by Iga Heinaizaemon No Jo Ienaga. Most famous in Bujinkan for the Kamayari, and jumping techniques.