Marine and continental deposits from the Tjornes area in northern Iceland were studied to obtain their pollen/spore content. Six Pollen Zones (PZ) were defined in the Early Pliocene Tjornes beds and the Early Pleistocene Breidavik Group. The pollen is most diverse during the deposition of the lowest Tapes Zone (PZ 1) and the lower part of the overlying Mactra Zone (PZ 2). Local pollen from marshland, levee and foothill forests was deposited on a large coastal plain. The pollen spectrum reflects transgression and deepening during the second part of the Mactra Zone (PZ 3) and the lower part of the Serripes Zone (PZ 4). Gymnosperm pollen derived from the higher inland plateau increases in PZ 3. This background pollen was of minor importance during periods with an extensive coastal plain (PZ 1, 2, 4, 6). PZ 5 did not yield sufficient pollen for analysis. The pollen analysis allowed refinement of the sea-level variations based on sedimentology and molluscs. Pollen of warmth-demanding plants is recorded throughout the Tjornes beds and the Early Pleistocene interglacial deposits. Warmth-loving species indicate summers 8 degrees C warmer than today during deposition of the Tapes Zone, and at least 5 degrees C warmer during the rest of the Tjornes beds. The Pliocene vegetation of Iceland matches well that of the present-day western European maritime temperate climate. The drastic cooling at the onset of the Quaternary led to a marked vegetation impoverishment, already noticeable in the Early Pleistocene Breidavik Group.