Diving with self-contained underwater breathing apparatus (SCUBA) induces endothelial dysfunction that seems to be an important factor in development of decompression sickness (1). Flow-mediated dilation (FMD) is a measure of endothelial function and is reported to be decreased following single and repetitive dives (2,3). An impaired endothelial function has also been observed following acute periods of oscillatory shear stress (OSI) in the conduit arteries, which induces the expression of pro-atherogenic factors (4). The aim of this study was to assess whether post-dive endothelial dysfunction could further be worsened with a short period of OSI. Twelve male divers (age 39.3±9.2 years, height 186±6 cm, weight 88.0±11.6 kg) completed a single dive to a depth of 18m sea water with a 47-min bottom time. Endothelium-dependent vasodilator function of the brachial artery was assessed pre- and post-intervention of imposed oscillatory shear stress by a 20-min cuff inflation to 75 mmHg over the forearm (5), using the FMD approach. All FMD measures were analysed by two-way repeated measure analysis of variance (RM-ANOVA; factors: time – pre-/post-intervention, condition – pre-/post-dive). There was an interaction effect for absolute and relative FMD (p=0.017 and p=0.009, respectively). Absolute FMD was reduced by 30.7±18.2% following the intervention (p<0.05), but only in the pre-dive condition. Diving reduced FMD by 24.1±11.9% (p<0.05) but there was no further reduction induced by the intervention. The interaction effect persisted following allometric scaling for baseline diameter and including SRAUC and baseline diameters as covariates (p=0.006). Endothelial function measured through FMD seems to be susceptible to oscillatory shear stress pre-dive, but the effect OSI is mitigated post-dive, as the values of FMD are already decreased by diving induced stress factors.