Conventional treatment for patients with community-acquired pneumonia (CAP), typically consists of parenteral antibiotic therapy for 7-10 days. However, clinical evidence shows that in most patients, the indicators of infection are substantially improved within the first 2 days of treatment. Thus, many of these patients can be switched to oral antibiotics. This treatment approach, known as sequential therapy which is defined as the early conversion from parenteral to oral antibiotics, decreases duration of hospitalization and cost of treatment. Based on this evidence, the aim this study was to evaluate the efficacy of sequential therapy and also the effects of this procedure on duration of hospitalization and cost of treatment in patients with CAP. 75 patients with CAP were divided randomly into 3 groups and sequential therapy was performed with penicillins (procaine penicillin + penicillin V) in the first group, cephalosporins (ceftriaxone + cefixime) in the second group and macrolides (clarithromycin) in the third group. In the patients who were clinically stable and whose fever and white blood cell count became normal, parenteral treatment was changed to oral treatment. The study was completed with 64 patients whose all controls could be done. Although there were no significant differences between study groups' either the duration of hospitalization or parenteral and total duration of treatment, the cost of treatment in group treated with penicillins was significantly lower when compared with the other groups. As a result, sequential therapy in CAP is an effective and trusty procedure which decreases duration of hospitalization and cost of treatment. In addition, it can be concluded that penicillins are still the cheapest and effective treatment choice in such kind of patients in our country.