Contest is a vitally important aspect of judo. Early examples include the Kodokan Monthly Tournament and the biannual Red and White Tournament, both of which started in 1884 and continue to the present day.
In 1899, Kano was asked to chair a committee of the Dai Nippon Butoku Kai to draw up the first formal set of contest rules for jujutsu. These rules were intended to cover contests between different various traditional schools of jujutsu as well as practitioners of Kodokan judo. Contests were 15 minutes long and were judged on the basis of nage waza and katame waza, excluding atemi waza. Wins were by two ippons, awarded for throwing that were the opponent's back strikes flat onto the mat or by pinning them on their back for a "sufficient" amount of time or by submission. Submissions could be achieved via shime-waza or kansetsu-waza. Finger, toe and ankle locks were prohibited. In 1900, these rules were adopted by the Kodokan with amendments made to prohibit all joint locks for kyu grades and added wrist locks to the prohibited kansetsu-waza for dan grades. It was also stated that the ratio of tachi-waza to ne-waza should be between 70% to 80% for kyu grades and 60% to 70% for dan grades.
In 1916, additional rulings were brought in to further limit kansetsu waza with the prohibition of ashi garami and neck locks, as well as does jime. These were further added to in 1925, in response to Kosen judo, which concentrated on ne waza at the expense of tachi waza. The new rules banned all remaining joint locks except those applied to the elbow and prohibited the dragging down of an opponent to enter ne waza.
The All-Japan Judo Championships were first held in 1930 and have been held every year, with the exception of the wartime period between 1941 and 1948, and continue to be the highest profile tournament in Japan.
Judo's international profile was boosted by the introduction of the World Judo Championships in 1956. The championships were initially a fairly small affair, with 31 athletes attending from 21 countries in the first year. Competitors were exclusively male until the introduction of the Women's Championships in 1980, which took place on alternate years to the Men's Championships. The championships were combined in 1987 to create an event that takes place annually, except for the years in which Olympic Games are held. Participation has steadily increased such that, in the most recent championships in 2011, 871 competitors from 132 countries took part.