There were also two guest teams each from the NIFL Premiership and Welsh Premier League, the first time the competition featured teams from outside Scottish football. The competition was first held during the 1990–91 season as the B&Q Centenary Cup to celebrate the 100th anniversary of the formation of the SFL and it was intended to be a one-off competition but was continued due to its popularity. The first winner of the tournament was Dundee, who defeated Ayr United, Falkirk are the most successful team in the tournament, with four wins, most recently in 2012. The most recent winner was Dundee United, who defeated St Mirren in the 2017 final, the Challenge Cup is a knock-out tournament. Within a regionalised format, clubs are paired at random and the first club drawn listed as the home team, the winner of each match progresses to the next round and the loser is eliminated from the tournament. Every match, including the final, is a tie that lasts 90 minutes plus any additional stoppage time. If no clear winner has been determined after 90 minutes of time,30 minutes of extra time is played. If the score is level after extra time then the winner is decided by a penalty shoot-out. Beginning with the 2016–17 season, the competition has expanded to 54 entrants. Teams are seeded to enter the competition over any of the first four rounds, the final is played at a neutral venue. The competition was created in the 1990–91 season to celebrate the 100th anniversary of the formation of the Scottish Football League in 1890 and it was intended to run for only one season but continued due to its popularity. This was reflected in attendances at matches in the later rounds of the tournament including a full capacity crowd of 11,500 at Fir Park in the first final. The cup was sponsored by DIY retail company B&Q and named the B&Q Centenary Cup for the first year, when Stenhousemuir won the final in 1995 it was regarded as the clubs greatest achievement in its 111-year history. The number of competitors has varied in relation to the number of clubs with Scottish Football League membership, before the change in 2010, several clubs received a random bye in the first round in order to even out the number of fixtures. The Challenge Cup continued under the auspices of the Scottish Professional Football League after the Scottish Football League merged with the Scottish Premier League in 2013 and this was simplified in the 2014–15 season, with the two additional places going to the Highland League champion and the Lowland League champion. Two teams from the League of Ireland will be included in the competition for the 2017–18 season, the final match of the tournament is played at a neutral venue, usually one that is geographically close or equidistant to where the clubs contesting the match are based. Eight different venues have hosted the final, Fir Park in Motherwell was the first, in 1990, and has since hosted four more finals, the last in 2017. McDiarmid Park in Perth has been the most frequent venue, staging it nine times between 1994 and 2015, other venues to host the final more than once are Broadwood Stadium, Excelsior Stadium and Almondvale Stadium
McDiarmid Park in Perth has hosted the final nine times, more times than any other venue.
Home improvement retailer B&Q were the first sponsors of the tournament, from 1990 until 1995.