 Netherlands: Rotterdam - Doubles - Main |
|---|
| 1/8-finals | Cash P./Casal S. | Mortensen M./Nijssen T. | 2:0 (6:4, 6:3) | details | 25.02.1991 |
 Germany: Stuttgart 1 - Doubles - Main |
|---|
| 1/8-finals | Mortensen M./Nijssen T. | Casal S./Sanchez E. | 1:2 (5:7, 7:6, 4:6) | details | 18.02.1991 |
| Netherlands: Hilversum - Doubles - Main |
|---|
| 1/8-finals | Mortensen M./Nijssen T. | Jaite M./Miniussi C. | 0:2 (4:6, 3:6) | details | 23.07.1990 |
| Germany: Stuttgart - Doubles - Main |
|---|
| 1/8-finals | Mortensen M./Nijssen T. | Henricsson P./Utgren N. | 0:2 (4:6, 5:7) | details | 18.07.1990 |
 United Kingdom: Wimbledon - Doubles - Main |
|---|
| 1/16-finals | Mortensen M./Nijssen T. | Ferreira W./Norval P. | 2:3 (4:6, 7:6, 6:4, 6:7, 7:9) | details | 01.07.1990 |
| 1/32-finals | Albano P./Engel D. | Mortensen M./Nijssen T. | 2:3 (5:7, 7:6, 6:3, 6:7, 4:6) | details | 30.06.1990 |
 France: French Open - Doubles - Main |
|---|
| 1/16-finals | Mortensen M./Nijssen T. | Haarhuis P./Koevermans M. | 1:2 (6:2, 3:6, 8:10) | details | 31.05.1990 |
| 1/32-finals | Davis S./Pate D. | Mortensen M./Nijssen T. | 1:2 (6:3, 1:6, 4:6) | details | 28.05.1990 |
 Italy: Rome - Doubles - Main |
|---|
| 1/16-finals | Mortensen M./Nijssen T. | Novacek K./Srejber M. | 0:2 (3:6, 2:6) | details | 14.05.1990 |
| Germany: Hamburg - Doubles - Main |
|---|
| 1/16-finals | Mortensen M./Nijssen T. | Bathman R./MacPherson D. | 0:2 (4:6, 5:7) | details | 07.05.1990 |
 USA: Miami - Doubles - Main |
|---|
| 1/32-finals | Mortensen M./Nijssen T. | Deppe R./Talbot B. | 0:2 (6:7, 3:6) | details | 16.03.1990 |
| Netherlands: Rotterdam - Doubles - Main |
|---|
| Semi-finals | Nargiso D./Pereira N. | Mortensen M./Nijssen T. | 2:0 (7:6, 6:4) | details | 03.03.1990 |
| Quarter-finals | Galbraith P./MacPherson D. | Mortensen M./Nijssen T. | 0:2 (3:6, 4:6) | details | 01.03.1990 |
| 1/8-finals | Mortensen M./Nijssen T. | Cherkasov A./Phillips R. | 2:0 (6:4, 6:1) | details | 26.02.1990 |
| Germany: Stuttgart 1 - Doubles - Main |
|---|
| Final | Forget G./Hlasek J. | Mortensen M./Nijssen T. | 2:0 (6:3, 6:2) | details | 25.02.1990 |
| Semi-finals | Becker B./Jelen E. | Mortensen M./Nijssen T. | WO. | details | 24.02.1990 |
| Quarter-finals | Mortensen M./Nijssen T. | Antonitsch A./Castle A. | 2:1 (7:6, 6:7, 6:4) | details | 21.02.1990 |
| 1/8-finals | Dyke B./Taroczy B. | Mortensen M./Nijssen T. | 1:2 (1:6, 7:6, 6:7) | details | 19.02.1990 |
