This study analyzed 415 patients with brucellosis in Tehran, Iran between 1998-2005. Most patients were female, aged 20-40 years, and had symptoms for less than 2 months. The most common symptoms were sweating and fever, while the most frequent signs were fever, arthritis, and splenomegaly. The majority of patients consumed non-pasteurized dairy products. Rifampin plus cotrimoxazole was the most common treatment, but resulted in the highest relapse rate, while doxycycline and cotrimoxazole led to the fewest relapses. Relapse remained a complication even following appropriate treatment.