The 12th South American Junior Championships in Athletics were held in São Paulo, Brazil, between December 15–17, 1978.

[1] Detailed result lists can be found on the "World Junior Athletics History" website.

[2] 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[3] and women[4] Complete results can be found on the "World Junior Athletics History" website.

[2] *   Host nation (Brazil)