Acute cholecystitis is a frequent cause of Acute Abdomen. For its diagnosis differnt methods both radiological and imaging are available. Ultrasound is considered as the method of choice in the primary evaluation of patient with right upper quadrant pain of the abdomen. Its advantages are: reliable, accesible, no invasive, quick and useful in pediatric patients and pregnant women. Sensitivity and specificity are high and is indepent with the liver function. The other methods of diagnosis are analized.