The effects of catalyst and duration of digestion on the crude protein content of various feed samples were studied with Kjeltec autosystem. Samples used for crude protein analysis were fish meal, soybean meal, concentrate mixture and commercial mixed feed. The crude protein content of each sample was determined using Hg, Cu or Se as a catalyst and the duration of digestion was 20, 40, 60 or 80 min. Also same samples were analyzed for crude protein at 11 different feed mills using the same three catalysts. A total of 17 feed mills equipped with a Kjeltec autosystem replied to the survey which was intended to find out user`s opinion on various aspects of this system. The followings are the results obtained from the studies 1. The results of protein analysis by Purina Korea using a Kjeltec autosystem showed that protein values were higher when Hg was used as a catalyst, followed by Cu and Se. also, protein values of the four feed samples increased with longer time of digestion. The Hg was proved to be the most effective catalyst for the digestion of feed sample except the commercial mixed feed. 2. Hg appears to be the most effective catalyst for crude protein analysis regardless of analytical system, followed by Cu and Se. Therefore, it is necessary to correct protein values obtained with different catalysts. The correction factors were determined for different protein content and for two different analytical systems. Optimum duration of digestion with Hg appears to be 40 min, and 60 min digestion may be required for proper protein analysis when Cu or Se is used as a catalyst. However, it may be safer to digest samples for 60 min or longer for complete recovery. 3. Crude protein values analyzed with Kjeltec autosystem from 11 feed mills were not affected by the kind of catalyst.