Sedimentological and radiocarbon investigations are part of an ongoing research on the Bay-head delta of northeast Guanabara Bay, Rio de Janeiro State. Sediment accumulation indicates that the Holocene infill of the bay-head delta started around 8.2 kyr BP and was not in pace with the eustatic sea-level rise. Sediment accumulation was faster during the transgressive phase (0.56 cm.yr-1). However, during the regressive phase, progradation driven by base-level fall was predominant over vertical sediment accumulation (0.02 cm.yr-1). Based on coring, three sedimentary units were defined: fluvial sands (U1), estuarine deposits (U2) and fluvial mud (U3).