An event is described as standing room only when it is so well-attended that all of the chairs in the venue are occupied, leaving only flat spaces of pavement or flooring for other attendees to stand. Some venues issue standing-room-only (or SRO) tickets for a reduced cost since it can become very uncomfortable to stand through the course of an event. However some fans actually prefer standing-room-only tickets as the crowds that gather can be more active than people who are sitting down for much of the event. Such crowds can become dangerous with the potential of riots and crushing movements occasionally occurring and resulting in death or injury.

For example, standing room only areas are very common at football matches across the globe and tickets sold as standing area tickets are sometimes the most popular, i.e. they are not sold merely when all seating tickets have been sold out. However, the periodic occurrence of tragedies related to standing room only areas at football matches such as at Hillsborough

Hillsborough disaster

The Hillsborough disaster was a human crush that occurred on 15 April 1989 at Hillsborough, a football stadium, the home of Sheffield Wednesday F.C. in Sheffield, England, resulting in the deaths of 96 people, and 766 being injured, all fans of Liverpool F.C....

 and Guatemala City have led to calls to eliminate such arrangements. In England, standing room, once a staple of most football stadiums there, has been practically eliminated at the highest level, all of the major stadiums have been refurbished as all-seaters.

Standing room has always been rare in the United States and Canada.

This term can also describe public transportation services that have extremely high riderships. In areas where there is a high risk of buses, etc. being a target of a terrorist bombing, buses may lack seats and be standing room only to eliminate hiding places.