Pain is the most important and current nursing diagnosis at I.C.U of heart surgery. So it must be relive for its acute complication. The purpose of this study was to compare nurses and patients perception of pain and its relation to analgesics in patients undergone coronary bypass surgery in one of the selected hospital in Iran    medical university in 2000 and to give some suggestions according to results of this study.

          This research was a descriptive study. In this study 30 patients with30 nurses caring of them in cardiac surgery I.C.U in one of the hospital of Iran medical university were participated .The materials in this study included question forms, scale of intensity of pain and analgesic dose check list. The first part included questions    related to personal specifications of nurses and patients participating in study. The  second part included 25 sentences about patients and nurses understanding of pain. For evaluating the degree of pain and severity of its perception in patients the statistical method was used. According to its"10" scores column the "o" was for no pain perception and "10" was for the most possible sense pain.

          The result of this study was summarized in 6 figures. The " T " statistical analysis showed that the patients average of pain perception was more than pain perception of nurses (P=0.001). The "pair t-test" detected significant differences between degree of perception of pain in patients before and after injection of    analgesics and also perception of patients pain in their nurses (P=0.001). In addition according to "t-test" there was significant differences between the degree of pain in patients and degree of perception of this pain in nurses before and after the injection of analgesics (P=0.001). But, there was no relation between dose of    analgesics with the patients’ and nurses’ perception of pain, and also the degree of patients pain before and after the injection of analgesics and degree of nurses perception of patients pain before and after the injection of analgesics.

          According that nurses’ perception of patients’ pain is an important factor in decision making strategy of pain relative; so the nurses must pay more attention to patients pain.