Judo will make its sixth Olympic appearance, but just the third for women. There are seven weight classes for men and women: extra lightweight, half lightweight, lightweight, half middleweight, middleweight, half heavyweight and heavyweight, which range from 132 1/4-220 1/2 pounds for men and 106-172 pounds for women. A judo match lasts five minutes for men and four for women. The object of judo is to score a full point of technical superiority, or ippon, during a five-minute match for men and four-minute match for women. An ippon is scored by a clean and forceful throw -- by holding the opponent mainly on his back for 30 seconds, under control but not necessarily immobile, or by submission to a strangle, a choke or a lock applied against the elbow. Waza-ari is scored by a throw not quite good enough for ippon or by a 25-second hold-down. Yuko and koka cam be scored for inferior throws or by 20- and 10-second hold-downs, respectively. A second waza-ari in a match counts as an ippon, but any amount of yukos is inferior to one waza-ari and any amount of kokas is inferior to one yuko. A competition for each weight class is held on one day from September 16-22 and will be held at the Sydney Exhibition Center, Halls 1 and 2.