| 26‑Nov‑1990 | Bossonnens CH | Hard | R32 | 201 | 285 | (WC)Roger Smith [BAH] d. Apell | 6-2 4-6 7-6 | | | | | | | | | |
| 24‑Sep‑1990 | Thessaloniki CH | Hard | R32 | 191 | 179 | (5)Gianluca Pozzi [ITA] d. Apell | 6-3 6-1 | | | | | | | | | |
| 17‑Sep‑1990 | Dijon CH | Carpet | SF | 226 | 181 | Henrik Holm [SWE] d. (LL)Apell | 7-6 6-0 | | | | | | | | | |
| 17‑Sep‑1990 | Dijon CH | Carpet | QF | 226 | 340 | (LL)Apell d. (Q)Michael Kupferschmid [GER] | 6-3 6-1 | | | | | | | | | |
| 17‑Sep‑1990 | Dijon CH | Carpet | R16 | 226 | 164 | (LL)Apell d. (7)Patrick Baur [GER] | 6-1 6-4 | | | | | | | | | |
| 17‑Sep‑1990 | Dijon CH | Carpet | R32 | 226 | 243 | (LL)Apell d. Bruce Derlin [NZL] | 6-4 4-6 6-2 | | | | | | | | | |
| 10‑Sep‑1990 | Azores CH | Hard | R16 | 234 | 169 | (4)Francisco Roig [ESP] d. Apell | 6-3 6-1 | | | | | | | | | |
| 10‑Sep‑1990 | Azores CH | Hard | R32 | 234 | 235 | Apell d. Scott Patridge [USA] | 6-4 6-4 | | | | | | | | | |
| 23‑Jul‑1990 | Hanko CH | Clay | R32 | 234 | 250 | Andres Vysand [GER] d. (LL)Apell | 6-4 6-4 | | | | | | | | | |
| 9‑Jul‑1990 | Bastad | Clay | R32 | 244 | 80 | Veli Paloheimo [FIN] d. (Q)Apell | 6-1 6-1 | | | | | | | | | |
| 28‑May‑1990 | Furth CH | Clay | QF | 279 | 409 | (Q)Felipe Rivera [CHI] d. (Q)Apell | 1-6 6-1 6-3 | | | | | | | | | |
| 28‑May‑1990 | Furth CH | Clay | R16 | 279 | 153 | (Q)Apell d. (2)Paul Vojtischek [GER] | 7-6 3-6 7-5 | | | | | | | | | |
| 28‑May‑1990 | Furth CH | Clay | R32 | 279 | 180 | (Q)Apell d. Chris Garner [USA] | 6-3 6-3 | | | | | | | | | |
| 7‑May‑1990 | Hamburg Masters | Clay | R64 | 298 | 91 | (WC)Udo Riglewski [GER] d. (Q)Apell | 6-1 6-2 | | | | | | | | | |