Background: The cytology and the support of clinical symptoms, biochemistry for diagnosis of the cases of effusions are very important. Objectives: - To describe some of clinical symptoms and biochemistry of effusions. - To compare the results between cytology and biochemistry by the causes of pleural, peritoneal fluids. Material & Method: A cross-sectional study to describe all of 47 patients with pleural, peritoneal effusions examinated by cytology in the Hospital of Hue University of Medicine and Pharmacy from April 2013 to January 2014. Results: In 47 cases with effusions, pleural effusion accounting for 55.32%, following peritoneal effusions 29.79% and 14.89% with both of them. The most common symptoms in patients with pleural effusions were diminished or absent tactile fremitus, dull percussion, diminished or absent breath sounds (100%), in patients with peritoneal effusions was ascites (95.24%). 100% cases with pleural effusions, 50% cases with peritoneal effusions and 80% cases with pleural and peritoneal effusions were exudates. The percentage of malignant cells in patients with pleural effusions was 26.92%, in peritoneal effusions was 28.57%, in pleural and peritoneal effusions was 42.86%. The percentage of detecting the malignant cells in patients with suspected cancer in the first test was 57.14%, in the second was 9.53% and 33.33% undetectable. Most of cases which had malignant cells and inflammatory were exudates, all of the cases which had a few cells were transudates. Besides, 7.5% cases which had high neutrophil leukocytes were transudates. Conclusion: Cytology should be carry out adding to the clinical examinations and biochemistry tests to have an exact diagnosis, especially for the malignant ones. For the case with suspected cancer, we should repeat cytology test one more time to increase the ability to detect malignant cells. Key words: Effusion, pleural effusion, peritoneal effusion, cytology, biochemistry