(super 87) Sr/ (super 86) Sr measurements were carried out on planktonic foraminiferal shell samples collected in the Early Pliocene succession of DSDP Site 132 (Tyrrhenian Sea, Western Mediterranean). The measured ratios range between 0.708980 and 0.709023, showing moderate fluctuations and a maximum variation of 0.000043 that falls within the uncertainty range of the Sr isotope measurements (+ or -0.000022) and suggests relatively constant ratios throughout this succession. The Mediterranean seawater (super 87) Sr/ (super 86) Sr ratios measured in a sample collected 55 cm above the Miocene/Pliocene Boundary and dated to 5.31+ or -0.01 Ma, are consistent with those measured in coeval oceanic successions, confirming the open marine depositional environment revealed by foraminiferal assemblages. The measured ratios are consistent with those collected in the Lower Pliocene deep sea sequence at Hole 654A (about 70 km NW from DSDP Site 132) and these are also comparable with other data from coeval oceanic and on land successions, taking into account the uncertainty of the Sr isotope measurements. The occurrence of relatively constant ratios throughout this succession, as previously shown in other coeval deep sea sequences of the Mediterranean and if verified in other successions, may hamper precise age determinations of the Early Pliocene marine carbonate in this basin.