| Game |
| Result | Moves |
Year |
Event/Locale | Opening |
| 26. A Jongsma vs Gufeld |
| 0-1 | 43 |
1961 |
WchT U26 08th | A45 Queen's Pawn Game |
| 27. B Brinck-Claussen vs A Jongsma |
| ½-½ | 28 |
1961 |
Helsinki | B93 Sicilian, Najdorf, 6.f4 |
| 28. A Jongsma vs C Kalme |
| 0-1 | 39 |
1961 |
WchT U26 08th | E70 King's Indian |
| 29. A Jongsma vs Kavalek |
| 1-0 | 58 |
1961 |
WchT U26 08th | A07 King's Indian Attack |
| 30. M Krajcsovits vs A Jongsma |
| 1-0 | 66 |
1961 |
WchT U26 08th | D32 Queen's Gambit Declined, Tarrasch |
| 31. G Kvist vs A Jongsma |
| ½-½ | 29 |
1961 |
WchT U26 08th | A07 King's Indian Attack |
| 32. A Jongsma vs P Troeger |
| 1-0 | 49 |
1962 |
Clare Benedict Cup 09th | A20 English |
| 33. A Jongsma vs H Steniczka |
| ½-½ | 40 |
1962 |
Clare Benedict Cup 09th | B05 Alekhine's Defense, Modern |
| 34. A Jongsma vs M Haygarth |
| 0-1 | 52 |
1962 |
Clare Benedict Cup 09th | A03 Bird's Opening |
| 35. P Puig Pulido vs A Jongsma |
| 1-0 | 57 |
1962 |
Clare Benedict Cup 09th | B22 Sicilian, Alapin |
| 36. O Marthaler vs A Jongsma |
| ½-½ | 34 |
1962 |
Clare Benedict Cup 09th | A46 Queen's Pawn Game |
| 37. Jansa vs A Jongsma |
| 1-0 | 28 |
1963 |
Budva | B33 Sicilian |
| 38. A Hollis vs A Jongsma |
| ½-½ | 48 |
1964 |
WchT U26 11th fin-B | A50 Queen's Pawn Game |
| 39. A Jongsma vs C B Van den Berg |
| 1-0 | 43 |
1965 |
NED-ch22 | A61 Benoni |
| 40. Gilg vs A Jongsma |
| ½-½ | 44 |
1967 |
OWL Ch | B32 Sicilian |
| 41. F Kuijpers vs A Jongsma |
 | 0-1 | 17 |
1968 |
IBM | B35 Sicilian, Accelerated Fianchetto, Modern Variation with Bc4 |
| 42. Ujtelky vs A Jongsma |
| ½-½ | 23 |
1968 |
Hoogovens-B | E09 Catalan, Closed |
| 43. Kotov vs A Jongsma |
| 1-0 | 86 |
1968 |
IBM | D80 Grunfeld |
| 44. A Jongsma vs Bronstein |
 | ½-½ | 41 |
1968 |
Amsterdam | B10 Caro-Kann |
| 45. Ivkov vs A Jongsma |
| ½-½ | 14 |
1968 |
Amsterdam IBM | A23 English, Bremen System, Keres Variation |
| 46. Timman vs A Jongsma |
| 1-0 | 41 |
1968 |
The Hague | A49 King's Indian, Fianchetto without c4 |
| 47. A Jongsma vs J Kozma |
| ½-½ | 24 |
1969 |
Hoogovens-B | B82 Sicilian, Scheveningen |
| 48. T Krabbe vs A Jongsma |
 | 1-0 | 47 |
1969 |
Wijk aan Zee II | B00 Uncommon King's Pawn Opening |
| 49. N Gaprindashvili vs A Jongsma |
| 1-0 | 37 |
1969 |
Beverwijk (Netherlands) | B29 Sicilian, Nimzovich-Rubinstein |
| 50. Ujtelky vs A Jongsma |
| 1-0 | 35 |
1969 |
Hoogovens-B | A20 English |