Crimean-Congo hemorrhagic fever was rarely reported from Iran before 1999. In a recent outbreak, the disease has been reported from different provinces of Iran, especially from Sistan and Baluchestan. Ribavirin has been recommended by World Health Organization as a potential therapeutic modality for Crimean-Congo hemorrhagic fever. This study was conducted to determine the clinical outcome and the effect of ribavirin in two groups of patients with Crimean-Congo hemorrhagic fever who were treated at different times. In this cross-sectional study, we evaluated patients with Crimean-Congo hemorrhagic fever who were admitted to Boo-Ali Hospital in Zahedan, a subtropical area in southeastern Iran, at the first three years after beginning of the last outbreak (1999 - 2003) and those who were admitted during 2005 - 2007. First, we found all patients with confirmed Crimean-Congo hemorrhagic fever infection who were treated with oral ribavirin. Then, they were evaluated for recovery and mortality rate. We evaluated 123 patients with confirmed Crimean-Congo hemorrhagic fever infection (91 patients treated between 1999 and 2003, and 32 patients between 2005 and 2007). Among the 91 patients, 73 (80%) survived, and 18 (20%) died of the disease. During 2005 - 2007, among the 32 patients who were treated within three days of onset of the disease, only one (3%) died of the disease. The recovery rate was higher among patients who were admitted during 2005 - 2007 than those hospitalized between 1999 and 2003 (97% vs. 80%). There was a significant (P=0.001) difference in the mortality rate between the two groups. Prompt treatment with oral ribavirin can increase the recovery rate in patients with Crimean-Congo hemorrhagic fever.