Siliceous microfossils exhibit an interesting pattern of occurrence in Integrated Ocean Drilling Program Expedition 342 sediments. A review of shipboard data from smear slides and microfossil processing notes was combined with shore-based investigations to provide a revised summary of this occurrence pattern. A review of radiolarian biostratigraphy was also undertaken for all sites. In general, siliceous microfossils (diatoms and radiolarians) are abundant and well preserved in lower Miocene and upper Oligocene drift sediments on the J-Anomaly Ridge (Sites U1404, U1405, and U1406) but are otherwise rare in Neogene to upper Eocene sediments from all sites. Siliceous microfossils (mainly radiolarians) are also abundant in middle Eocene to upper lower Eocene sediments at several sites, tending to be more persistent in the deeper J-Anomaly Ridge sites (U1403 and U1404) than in the shallower sites (U1406 and U1407) and all southeast Newfoundland ridge sites (U1408, U1409, and U1410). No siliceous microfossils were encountered at Site U1411. Sediments are chert rich through the Paleocene-Eocene transition at Sites U1403 and U1407, and as a consequence siliceous microfossils are frequently abundant but always poorly preserved. Well-preserved radiolarians occur in the upper and middle Paleocene at Sites U1403 and U1406-U1409. Hopefully, this record of siliceous microfossil abundance will be helpful in ongoing studies of biosiliceous sedimentation.