Input from alien cultures might stimulate exceptional national achievements. This hypothesis was tested by applying generational time-series analysis to a society whose history shows tremendous variation in its receptiveness to the external world (viz., Japan between 580 and 1939). After required controls and data transformations were introduced, the cross-correlations were examined between 3 measures of extracultural influx (outside influence, travel abroad, and eminent immigrants) and 14 measures of national achievement (politics, war, business, religion, medicine, philosophy, nonfiction, fiction, poetry, drama, painting, sculpture, ceramics, and swords). For most domains of creative achievement, the number of eminent individuals at generation g was a positive function of the amount of foreign influence at generation g – 2. For many leadership domains, in contrast, activity at generation g tended to be positively associated with national openness to alien influences at g + 1.