| In force components | 
| Number 
 | Title | Status | 
| Q.931 (05/98) 
 | ISDN user-network interface layer 3 specification for basic call control | In force 
 | 
| Q.931 (1998) Erratum 1 (02/03) 
 |  | In force 
 | 
| Q.931/I.451 (1998) Amendment 2 (12/23) 
 | Extensions for the support for the calling line identification authentication | In force 
 | 
| Q.931 (1998) Amendment 1 (12/02) 
 | Extensions for the support of digital multiplexing equipment | In force 
 | 
| 
 | 
| Superseded and Withdrawn components | 
| Number 
 | Title | Status | 
| Q.931/I.451 (11/88) 
 | ISDN user-network interface layer 3 specification for basic call control This Recommendation is also included but not published in I series under alias number I.451
 | Superseded 
 | 
| Q.931 (03/93) 
 | ISDN user-network interface layer 3 specification for basic call control This Recommendation is also included but not published in I series under alias number I.451
 | Superseded 
 |