The interface between acute hospital care and residential aged care has long been recognised as an important issue in aged care services research. Investigations into the feasibility of linking hospital morbidity and residential aged care data to examine the interface between the two sectors using linkage keys which did not include name, part of name or person identifier were conducted in 2001 and 2002. This paper employs statistical theory to establish why and under what circumstances the no-name strategy developed in the feasibility study is useful, and using these results refines the strategy for use in future work.