In order to assess the accuracy and regional significance of salt-marsh reconstructions of former sea level based on foraminiferal transfer functions, we compared the calibration of the foraminiferal assemblages of two salt-marsh cores from two estuaries using the regional transfer function constructed for the southern Bay of Biscay. The foraminifera-based reconstructions were placed into a temporal framework using ¹³⁷Cs, heavy metal concentrations, and ²¹⁰Pb-derived sediment accumulation rates. The resulting relative sea-level (RSL) curves were compared with the nearest tide-gauge data (Santander). The two RSL trends from core sediments show excellent agreement and are in very good agreement with instrumental data, providing a regional relative sea-level rise of 1.9 mm yr^-1 for the 20th century.