Reducing the numbers of coronary care unit (CCU) beds would decrease expensive unnecessary admissions, but might also block appropriate admissions. To study how physicians adapt to limited CCU beds, we compared their decisions to admit patients to the CCU when the CCU was full with those made when the CCU was not full. We studied 4479 patients who presented with symptoms suggesting acute cardiac ischemia to six New England hospital emergency rooms over 16 months. Of the 2931 patients found on follow-up not to have acute ischemia, 33% of those presenting when the CCU was not full were admitted to the CCU vs 24% of such patients presenting when the CCU was full (P = .0005), a 27% drop. Of the 725 patients proving to have angina pectoris, 74% of those presenting when the CCU was not full were admitted to the CCU vs 62% of such patients presenting when the CCU was full (P = .007), a 16% reduction. Of the 823 patients found to have myocardial infarction, 90% were admitted to the CCU both when the CCU was not full and when it was full. Importantly, for no group did mortality increase when the CCU was full. These data suggest that physicians can safely adapt to substantial reductions in the availability of CCU beds.