| Game |
| Result | Moves |
Year | Event/Locale | Opening |
| 26. C Lutz vs C Costello |
 | 1-0 | 18 | 1992 | Ostend Open | C17 French, Winawer, Advance |
| 27. O Prestel vs C Costello |
| 0-1 | 30 | 1993 | Neuwied op | A00 Uncommon Opening |
| 28. I Farago vs C Costello |
| 1-0 | 35 | 1993 | Neuwied op | D67 Queen's Gambit Declined, Orthodox Defense, Bd3 line |
| 29. A Jossien vs C Costello |
| ½-½ | 52 | 1993 | Cappelle Open | C69 Ruy Lopez, Exchange, Gligoric Variation |
| 30. T Levers vs C Costello |
| ½-½ | 59 | 1993 | Cappelle Open | C18 French, Winawer |
| 31. A Haouari vs C Costello |
| 1-0 | 39 | 1993 | Cappelle Open | C10 French |
| 32. M Gourmelen vs C Costello |
| ½-½ | 57 | 1993 | Cappelle Open | C30 King's Gambit Declined |
| 33. C Costello vs J Gdanski |
| 0-1 | 37 | 1993 | Cappelle Open | A37 English, Symmetrical |
| 34. J Ervinck vs C Costello |
| ½-½ | 49 | 1993 | Cappelle Open | C26 Vienna |
| 35. C Costello vs A F Wright |
| 1-0 | 64 | 1993 | Dublin Zonal | A16 English |
| 36. C Costello vs A Summerscale |
| 0-1 | 35 | 1993 | Dublin Zonal | D31 Queen's Gambit Declined |
| 37. K Arkell vs C Costello |
| 1-0 | 47 | 1993 | Dublin Zonal | D50 Queen's Gambit Declined |
| 38. C Costello vs B Lyons |
| 1-0 | 32 | 1993 | Dublin Zonal | A95 Dutch, Stonewall |
| 39. C Barry vs C Costello |
| 1-0 | 33 | 1993 | Dublin Zonal | C53 Giuoco Piano |
| 40. K Moynihan vs C Costello |
| 0-1 | 52 | 1993 | Dublin Zonal | D35 Queen's Gambit Declined |
| 41. C Costello vs S Brady |
| 0-1 | 31 | 1993 | Dublin Zonal | A35 English, Symmetrical |
| 42. C Costello vs M Waters |
| 0-1 | 28 | 1993 | Dublin Zonal | A21 English |
| 43. C Njotea vs C Costello |
| 1-0 | 41 | 1993 | Dublin Zonal | C69 Ruy Lopez, Exchange, Gligoric Variation |
| 44. D Roberts vs C Costello |
| 0-1 | 59 | 1993 | Dublin Zonal | C09 French, Tarrasch, Open Variation, Main line |
| 45. C Costello vs B Palmer |
| 0-1 | 44 | 1993 | Dublin Zonal | A13 English |
| 46. C Costello vs P Boersma |
| ½-½ | 26 | 1993 | Leeuwarden Open | A21 English |
| 47. H Jonkman vs C Costello |
| 1-0 | 36 | 1993 | Leeuwarden Open | C02 French, Advance |
| 48. C Costello vs H Klip |
| 0-1 | 28 | 1993 | Leeuwarden Open | A10 English |
| 49. M Kremer vs C Costello |
| 1-0 | 38 | 1993 | Leeuwarden Open | C18 French, Winawer |
| 50. K Kluss vs C Costello |
| 0-1 | 38 | 1993 | Leeuwarden Open | D62 Queen's Gambit Declined, Orthodox, Rubinstein Attack |
Kibitzing
