| Adept Technology Group Plc | Telecomms | Adept Technology Group Plc | 
| Admiral Group | Nonlife Insurance | Admiral Group | 
| AdvancedAdvT Limited | Automobiles & Parts | AdvancedAdvT Limited | 
| Advanced Medical Solutions Group | Pharmaceuticals & Biotechnology | Advanced Medical Solutions Group | 
| Aegis Group plc | Media | Aegis Group plc | 
| Aeorema Communications Group Plc | Media | Aeorema Communications Group Plc | 
| AEW UK REIT Plc | Real Estate Investment Trusts | AEW UK REIT Plc | 
| AFC Energy Plc | Energy | AFC Energy Plc | 
| Aferian Plc | Software & Computer Services | Aferian Plc | 
| Afh Financial Group Plc | Financial Services | Afh Financial Group Plc | 
| Afren | Oil & Gas Producers | Afren | 
| A.G. Barr plc | Beverages | A.G. Barr plc | 
| Aggreko plc | Support Services | Aggreko plc | 
| Agronomics Limited | Unknown | Agronomics Limited | 
| Airea Plc | Home Construction | Airea Plc | 
| Air Partner | Travel & Leisure | Air Partner | 
| Airtel Africa Plc | Telecomms | Airtel Africa Plc | 
| AJ Bell plc | Financial Services | AJ Bell plc | 
| Alba Mineral Resources | Mining | Alba Mineral Resources | 
| Albion Crown VCT Plc | Venture Capital Trusts | Albion Crown VCT Plc | 
| Albion Development VCT Plc | Venture Capital Trusts | Albion Development VCT Plc | 
| Albion Enterprise VCT Plc | Venture Capital Trusts | Albion Enterprise VCT Plc | 
| Albion KAY VCT Plc | Venture Capital Trusts | Albion KAY VCT Plc | 
| Albion Technology & General VCT Plc | Venture Capital Trusts | Albion Technology & General VCT Plc | 
| Albion Venture Capital Trust Plc | Unknown | Albion Venture Capital Trust Plc | 
| Aldermore Group | Banks | Aldermore Group | 
| Alent | Chemicals | Alent | 
| Alfa Financial Software Holdings Plc | Software & Computer Services | Alfa Financial Software Holdings Plc | 
| Alien Metals Limited | Industrial Metals | Alien Metals Limited | 
| Alliance Pharma plc | Pharmaceuticals & Biotechnology | Alliance Pharma plc |