Thermal management of data centers is an important issue for many high technology companies. The power requirement to provide proper indoor climate in data centers is considerable. Thus, possibilities for energy savings and efficient electricity utilization are quite important. In this paper, the airflow and temperature patterns, as well as the electrical power requirement within a small data center, have been investigated. The power requirement within the data center is considerably high, due to an oversized air conditioning system. An infrared camera was used to visualize the airflow and temperature pattern, showing that cool air does not reach the upper levels of the racks, despite a very high air exchange rate. Point measurements of temperatures in a rack show that recirculation cells are present, causing accumulation of heat and improper cooling of electronic equipments. Thus, the chilled air is not distributed properly and consequently the cooling energy is not used effectively. © 2005 Elsevier B.V. All rights reserved.