The world's largest privately owned and operated fitness center chain, 24 Hour Fitness was started in 1983 with a single California location. It has since grown to include over 340 current locations, with more than 3 million members. Most clubs are located in the West or Mid-West United States. The centers are designed to meet the requirements of a broad range of people, regardless of age, physical condition, or ability. They offer free weights, cardiovascular machines, classes, personal training, information resources, and advanced fitness equipment. They have varying sized clubs in different locales, differentiated by names including the Active Club, the Sports Club, and the Super Sport Club.

• Most 24 Hour Active Clubs are less than 25,000 square feet in size, and offer weight training, cardio equipment and fitness gear, with locker rooms and sometimes baby-sitting accommodations.
• The 24 Hour Fitness Sport clubs are usually over 35,000 square feet and may offer pools, basketball, sauna and steam rooms, juice bars, and Kids’ Clubs.
• The 24 Hour Fitness Super-Sport Club locations are generally over 50,000 square feet. In addition to the Sport Club features, they can have additional features like larger group exercise rooms and classes. Ultra-Sport locations are over 100,000 square feet, offer executive locker rooms, day spas, towel services, whirlpools, rock climbing walls, and racquetball courts.

A yearly contract is not required at 24 Hour Fitness, but an advance notice of 30 business days is necessary for membership cancellation. Enrollment fees vary from $50 to $179, with a $79 processing fee and monthly dues ranging from $40 to $60, depending on the location and its size. Also offered are 10 Day Free Trials, and 90 Day passes for $149 that allow you to try out the services. Despite its name, many 24 Hour Fitness clubs are not open 24 hours a day. So if you are hoping to avoid the rush by working out late at night, make sure you check the schedule before joining.