Purpose : The purpose of this study was to analyze the trend of the number of nursing staffs and skill mix and to assess the effectiveness of hospital nurse expansion policies in Korea. Methods : The trend of the number of nursing staffs and skill mix were analyzed using time series data, which composed of yearly series data from 1975 to 2009. The impact of hospital nurse expansion policies was estimated by autoregressive integrated moving average(ARIMA) intervention model. Results : The number of general hospital and hospital nurses per 100 beds was decreased in late 1980s and late 1990s due to rapid growth of beds. As a result of the number of nurse aids per 100 beds decreased, skill mix became high in general hospital but nurse ratio among hospital nursing staffs was about 50%. Expansion of new nurse and revised differentiated inpatient fee were only effective in expansion of hospital nursing staffs. But they had no effect in general hospitals. Conclusion : In Korea, a few policies related to expansion of hospital nurses have an effect on increasing the number of hospital nurse. Nevertheless, level of hospital nursing staffs is inferior to that of general hospital.