Multidisciplinary investigations of a radiocarbon dated isostatically raised, shallow marine sequence have enabled environmental parameters, including estimates of relative sea level and water temperatures, to be reconstructed for the Windermere Interstadial (WI) in the western Forth valley. Detailed faunal (ostracod and macrofauna) and sedimentological (particle size and micromorphology) examination of the 2.28 m sequence at Moss-side of Boquhapple suggests the existence of a shallow fjord-style margin environment at the site. Comparisons between recent faunal analogues and the fossil record suggest that WI relative sea levels can be limited to between +15 and +30 m OD. Additional regional stratigraphical and geomorphological investigations augment this interpretation. New AMS 14C dates suggest that marine accumulation at the site was established by c. 12.8 ka bp, and continued to probably after c. 11.5 ka bp. Palaeotemperature reconstructions from the macrofauna and ostracod records show some divergence, but suggest temperatures were lower than present. The upper 0.50 m of the sequence shows significant reworking, and micromorphological analysis of one sample from this marine deposit discloses a limited number of features consistent with subaerial (possibly periglacial) processes. The final lowering in relative sea level, possibly to below +7 m OD, is believed to have occurred during the Loch Lomond (Younger Dryas) Stadial.