During spring 1994 and summer 1995 hydrographic transects across thePorcupine Bank, an elliptical topographic structure adjoining the shelf-edge west ofIreland, were carried out to investigate the mass and flow field characteristics in thevicinity of the bank. The observations show a dome-like deformationof the temperature and density field together with an intrusion of cold, densewater above the bank summit. The dome-like perturbation of the mass field isaccompanied by an anti-cyclonic circulation along the flanks of the bank,which is evident during all observational periods. Its intensity varies stronglyin accordance with the strength of the background stratification. The currentfield results either fromTaylor cap formation above a topographic singularity in a steady flow or due tonon-linear rectification of topographically trapped waves through resonance with thediurnal tide. It is suggested, that the flow field at Porcupine Bank providesan important mechanism for the retentionof pelagic eggs and larvae of various marine species spawning in the area.