Global warming gives rise to higher probability of extreme temperature values and related events. Social and environmental impacts of these events are great at local scale. Most of the research that has been done on this issue in different countries denotes decrease of cold extremes and increase of warm extremes. To examine such changes, we used daily temperature data in 1951-2003 Period from 27 Iranian synoptic stations that have homogenous and high quality data and covering standard normal period (base period) 1961-1990. We used extreme temperature indices in five categories of percentile-based, absolute, threshold, duration, and other ones.Some of our obtained results show negative trends for extreme indices like number of frost days (FD), number of ice days (ID), cool days (TX10p), and cool nights (TN10p) in most stations under study. For instance, decrease of 8 to 10 frost days per decade in the northeast of the country is noteworthy. Conversely, we got positive trends for indices such as summer days (SU25), warm days (TX90p), and warm nights (TN90p) in most stations under study. Increases of 5 to 7 warm days per decade in Shiraz and Tehran are remarkable. We found all three behaviors of stationarity, positive and negative trends for indices such as warm and cold spell duration indices (WSDI and CSDI). Compared to other indices, spatial and temporal changes of the above two indices could not be interpreted well. Apart from some exceptions, our results were in agreement with the latest findings of Intergovernmental Panel on Climate Change (IPCC) and other worldwide studies.