Background: Acid-base disturbances are common in critically ill patients and pose a great burden in the management of the underlying condition. Aim: To explore the common types of acid-base disturbances among the critically ill patients in ICU. Design: A descriptive study design was utilized. Setting: This study was  carried out in the Trauma and general Intensive Care Units at Assiut university hospital. Sample: Eighty adult male and female patients admitted to trauma and general ICUs. Tools: Three tools were used in this study, patient assessment tool, APACHE II tool, and Acid-base parameters assessment tool. Result: Eighty patients suffered from acid-base disorders with mean age (41.88 ±13.39) years. The mean pH on admission was (7.34 ±0.13), the mean length of ICU stay was (10.90 ±7.86). Respiratory alkalosis was the most frequent of simple acid-base disturbance (73.8%) followed by metabolic alkalosis (33.8%), respiratory acidosis (32.5%). Mixed acid-base disorders were relatively less frequent, the common combination was metabolic acidosis with respiratory acidosis (15.0%). Conclusion: Acid-base disturbance are common among critically ill patients presenting at the ICU. Respiratory alkalosis was the most frequent simple acid-base disturbance was observed among such group of patients. Recommendation: Acid-base disturbance should be monitored closely, diagnosed early, and managed correctly during hospitalization