| XII South American Junior Championships in Athletics | |
| Size: | 200px |
| Host City: | São Paulo, Brazil  |
| Dates: | December 15–17 |
| Nations Participating: | 8 |
| Athletes Participating: | about 178 |
| Events: | 34 |
| Level: | Junior |
| Previous: | 1976 Maracaibo |
| Next: | 1980 Santiago |
The 12th South American Junior Championships in Athletics were held in São Paulo, Brazil, between December 15–17, 1978.
Detailed result lists can be found on the "World Junior Athletics History" website. An unofficial count yields the number of about 178 athletes from about 8 countries: Argentina (33), Bolivia (6), Brazil (53), Chile (42), Colombia (13), Paraguay (8), Peru (9), Uruguay (14).
Medal winners are published for men and womenComplete results can be found on the "World Junior Athletics History" website.
| 100 metres | 10.6 | 10.6 | 10.8 | ||||
| 200 metres | 22.0 | 22.1 | 22.5 | ||||
| 400 metres | 46.7 | 48.2 | 48.3 | ||||
| 800 metres | 1:50.3 | 1:50.9 | 1:51.0 | ||||
| 1500 metres | 3:58.9 | 3:59.2 | 3:59.5 | ||||
| 5000 metres | 14:53.0 | 14:57.2 | 15:16.5 | ||||
| 2000 metres steeplechase | 6:01.2 | 6:04.6 | 6:04.6 | ||||
| 110 metres hurdles | 14.6 | 14.8 | 15.2 | ||||
| 400 metres hurdles | 53.0 | 55.4 | 55.4 | ||||
| High jump | 2.00 | 2.00 | 2.00 | ||||
| Pole vault | 4.45 | 4.20 | 4.00 | ||||
| Long jump | 7.07 | 6.82 | 6.82 | ||||
| Triple jump | 14.86 | 14.72 | 14.72 | ||||
| Shot put | 16.50 | 16.20 | 15.92 | ||||
| Discus throw | 46.28 | 43.52 | 43.34 | ||||
| Hammer throw | 56.38 | 55.66 | 52.32 | ||||
| Javelin throw | 65.12 | 62.42 | 59.06 | ||||
| Decathlon | 6391 | 6254 | 6128 | ||||
| 4 × 100 metres relay | 41.6 | 42.0 | 42.0 | ||||
| 4 × 400 metres relay | 3:15.8 | 3:16.9 | 3:17.4 |
| 100 metres | 12.4 | 12.4 | 12.4 | ||||
| 200 metres | 25.5 | 25.7 | 25.9 | ||||
| 400 metres | 55.9 | 56.6 | 57.7 | ||||
| 800 metres | 2:11.9 | 2:13.0 | 2:13.0 | ||||
| 1500 metres | 4:36.3 | 4:36.9 | 4:41.1 | ||||
| 100 metres hurdles | 14.6 | 15.1 | 15.1 | ||||
| High jump | 1.70 | 1.65 | 1.65 | ||||
| Long jump | 5.67 | 5.56 | 5.55 | ||||
| Shot put | 12.42 | 12.41 | 12.05 | ||||
| Discus throw | 39.60 | 39.16 | 38.74 | ||||
| Javelin throw | 44.40 | 43.32 | 41.96 | ||||
| Pentathlon | 3712 | 3490 | 3242 | ||||
| 4 × 100 metres relay | 48.1 | 48.1 | 48.2 | ||||
| 4 × 400 metres relay | 3:47.3 | 3:47.8 | 3:56.8 |