Pliocene to Pleistocene planktonic foraminifers from Holes 1039B and 1043A have been quantitatively analyzed. In Zone N19, few occurrences of planktonic foraminifers and an abruptly decreasing ratio of warm-water planktonic foraminifers are recognized. This suggests that drops of the surface seawater temperature in Zone N19 are dated at 4.2-3.95 Ma in Hole 1039B and 5-4.2 Ma in Hole 1043A. G. sacculifer, a high salinity-tolerant species, is rarely found in Zone N19; therefore, no salinity change is recognized on the East Pacific side. The divergence of both surface- and intermediate-water dwellers is recognized around the top of Zone N21 in Hole 1039B. In Hole 1043A, the divergence is recognized in two horizons, that is from Zone N17 to the lower part of Zone N18 and the upper part of Zone N21. These changes in the planktonic foraminiferal assemblages might be related to the closing of the Central American Seaway. The maximum divergence of both surface- and intermediate-water dwellers in the basal part of Zone N22 might also be related to the final phase of the closing of the Central American Seaway.