We present the results of optical dating of quartz from marine and aeolian deposits on St. Agnes Island, Scilly Isles, UK. The single-aliquot regenerative-dose protocol was used to estimate the equivalent dose in these samples. Proposed tsunami-laid deposits at Big Pool provided ages of 230±40 and 380±60 years; both are consistent with an expected age of 244 years. An OSL age of 6±3 years was obtained on a modern sub-aqueous beach deposit. These results suggest that the OSL signal in the tsunami-laid quartz was completely reset before deposition, and that these sediments can be dated accurately by optical dating techniques. Sand dunes at Bergecooth, 250 m south of Big Pool, were also dated using OSL. These ages indicate phases of aeolian activity at ̃300 a and 1000 a in the Scilly Isles.