A total of 69 species of lichens have been collected from various locations around New Zealand. Screening of extracts of these species for antimicrobial, antiviral and cytotoxic activity showed a high proportion with biological activity. Active extracts were generally from species known to contain phenolic compounds. Bioactivity-directed isolation work on Cladia retipora, Pseudocyphellaria glabra and P. homoeophylla led to the identification of usnic acid as the main antimicrobial, cytotoxic and antiviral component in these three species.