11th Battalion, Ulster Defence Regiment

Mahon Barracks, Portadown. – a mixture of regular army and permanent cadre/part-time administration staff, instructors, watchkeepers, mechanics, and a guard force of Conrate soldiers. The commander was the battalion commander who was a regular lieutenant colonel. Other regular soldiers on attachment included the adjutant (a major), a training major, and permanent staff instructors. The Quartermaster's stores were also part of this company as were the core services of the battalion which, although modified slightly on expansion, generally consisted of operational organisation, vehicles, radio services, catering and pay.

Scarva Road Barracks, Banbridge – an experimental permanent cadre platoon formed after Ulsterisation which carried out the same duties as the regular army. Selected from the youngest and fittest soldiers with Commanders and NCO's who had, where possible, previous military experience. The commander was a Scottish WO2 who had 22 years of experience with the Royal Highland Fusiliers, fighting in colonial conflicts during the disestablishment of empire. His second in command was Colour Sergeant Robert (Bob) Beattie (Father of Captain Doug Beattie) who had fought in the Congo Crisis and in Cyprus with the Royal Ulster Rifles. The main duties were to quickly seal off the A1 Belfast – Dublin dual carriageway and to act as Quick Reaction Force (QRF) for 3 Infantry Brigade and RUC J Division. As the number of permanent cadre soldiers grew a new full-time company was formed at Portadown and the Operations Platoon was integrated into it taking the designation A Company.

Based at Mahon Barracks – a part-time company. Later renamed B Company. Drawn from men (and later women) from the village of Tandragee and the surrounding area this company came on duty at 7 pm on weekdays and all day on weekends. In addition to patrolling their own villages and rural areas, they were also responsible for the relief of the regular army on the permanent guard post at Tandragee Power Station.

(Dromore) was never formed but the designation was later given to A (Tandragee) Coy when the full-time rifle company was established at Portadown from the Operations Platoon and designated "A Company".

Kitchen Hill Barracks, Lurgan. – a part-time company with a small permanent cadre staff who ran the UDR centre within the regular army's barracks. This company was responsible for patrolling the town of Lurgan and its surrounding villages and rural areas.

Subsequent to a raid against C Company, on 20 October 1972, the guard commander Sgt Billy Hanna MM was convicted of supplying information to loyalist paramilitaries.[5] Most were recovered in follow up operations but some were later proven to have been used by loyalist organisations to carry out crime, including murders.[6]

Scarva Road Barracks, Banbridge – a part-time company with a small permanent cadre staff who administered and guarded the barracks. Drawing its recruits from Banbridge, Dromore and surrounding rural villages and areas the company also patrolled these areas and provided extra checkpoints on the A1 dual carriageway.

The gated off centre of Portadown - guarded by E Coy, 11UDR

A part-time company with a small nucleus of permanent cadre administrative staff drawn from the market town of Portadown and its surrounding villages and rural areas. The company provided patrols in the town and surrounding areas as well as the night guard on the telephone exchange at Edenderry.

After the amalgamation of 1 and 9 UDR in 1984[7] – a part-time company with a small nucleus of permanent cadre administration staff who ran the company offices and facilities within Thiepval Barracks. Recruiting from Lisburn and surrounding areas it too had a mixed patrol area of towns and villages but by its location also patrolled areas of south Belfast.