Molecular and morphological parameters of Serpula lacrymans isolates from various sites in the built environment in Europe and Australia were compared to similar parameters of ‘wild’ isolates from India, the Sumava Mountains (Czech Republic) and Mount Shasta (USA). The Indian, Czech Republic and all of the building isolates bar one showed identity in both molecular and morphological features. The Australian and the USA isolates (BF-050 and USA'94 respectively) showed specific morphological differences and could be separated on the basis of randomly amplified polymorphic deoxyribonucleic acid polymerase chain reaction (RAPD PCR) with the USA isolate being least closely related to the S. lacrymans type strain of FPRL12C. ITS sequence data revealed two base differences between FPRL12C and BF-050 in the 673 sequenced, nine differences between FPRL12C and USA'94 and 16 differences between USA'94 and the closely related organism Serpula himantioides. The possible evolutionary relationships between the various isolates are discussed along with suggestions for the origin of S. lacrymans as a scourge of the built environment in many temperate areas of the world.