The actor visited the Central African country this week to tour refugee camps and meet with aid officials and experts.
It is his fourth visit since 2007. In May he filmed a documentary on eastern Congo's difficulties for the news show "Nightline."
Affleck said he first became interested in Congo a few years ago, when Hollywood's attentions began to focus another African crisis, Darfur.
After doing more research, he says he was shocked to learn about Congo's four-year war, during which an estimated 5 million people died.
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