The shallow subtidal zone of SE Australia is dominated by urchin-grazed barrens, created and maintained by a large urchin, Centrostephanus rodgersii (A. Agassiz). We sought to determine how benthic invertebrates, such as sponges and colonial ascidians, maintain space in the face of this intense grazing pressure. Our data indicate that the cover of invertebrates on vertical substrata was positively correlated with the density of a large barnacle Aiistrobatanus Imperator and are consistent with this barnacle providing a refuge from urchin grazing. The exception was the common sponge Clathriapyramida which showed a strong negative relationship with barnacle density. We speculate that as aggregations of barnacles may represent foci for competitive interactions among sessile invertebrates, C. pyramida seeks to avoid these sites. It appears that recruitment of A. Imperator is sporadic and hence the conditions which allow the establishment of high densities of this barnacle remain unclear. As our data are correlative they must be interpreted cautiously. Experimental manipulation of barnacle density will provide a much clearer indication of the role of A.imperator in structuring these communities and is the focus of current work. D Porifera, Crustacea, Echinodermata, grazing réfugia, structural habitat complexity, urchin grazing, Clathria pyramida.