The UFC has implemented the Interim Title on several occasions in the past. The first time the UFC used the Interim Title was back in June of 2003 when Randy Couture fought Chuck Liddell for the title since Tito was in limbo with the UFC brass and had not had a fight in about a year. Randy went on to win the fight and 3 months later Randy defeated Tito to become the undisputed UFC LHW Champion.

The next time the title was used was when Frank Mir, who just defeated Tim Silvia, was not able to defend the title due to the injuries he sustained in a motorcycle accident. On February 2005, Andrei Arlovski fought Justin Eilers at UFC 53 for the Interim HW title. Arlovski won the fight and in August 2005, the title was changed to the undisputed champion due to Frank’s uncertain future in the division. The title was only promoted to undisputed after it became clear that Frank may never come back and needed to move the division along without him. 
In UFC 81, Antônio Rodrigo Nogueira would face off against Tim Sylvia for another Interim Title while the UFC and Randy Couture worked out their differences. Once those differences were worked out and Randy signed a new contract with the UFC, he made his title defense against Brock Lesnar at UFC 91, where he lost the title in the second round by TKO. 
Once again, the HW division needed to crown an Interim champ when Brock Lesnar became seriously ill as a result of his coming down with Diverticulitis. The UFC set up a fight between Frank Mir with Shane Carwin only to lose by KO in under 4 minutes. Then about three months later. Finally, when Lesnar was healed and ready to unify the titles, Carwin and Lesnar met at UFC 116 in the MGM Grand Garden Arena where Brock Lesnar was once again the undisputed UFC HW Champion. 
The WW division also had to use the Interim belt back in 2007 when Matt Serra had a herniated disc in his lower back. With Serra being out of the fight, the UFC put the Interim Title up for a fight between two former champions, Matt Hughes and Georges St. Pierre. Georges St. Pierre would end up submitting Hughes late in the second round to secure his chance to regain the title from Matt Serra when he became healthy and he did just that in UFC 83.
This brings us to the current situation with the UFC WW title picture. Georges St. Pierre has been the champion of the division since April 19th 2008. He is also a 2 time champion in the division with only 2 blemishes on his record. The first being, his title fight loss to Matt Hughes via arm bar at UFC 50 and then his TKO loss to Matt Serra at UFC 69. This is the first time, since Randy defeated Chuck at UFC 43, the Interim Title been used for a long time Champ. Most of the time, the title has been used for fighters that haven’t been the champion for a long time; however, this is not the case for the current UFC Interim WW Champion.