A large number of micro-organisms were cultured from marine substrates collected from multiple sites along the coast of the South Island of New Zealand. Depending on growth rate and colony morphology the micro-organisms were classified as terrestrial, facultative marine or obligate marine. Micro-organisms were selected for large scale culture and extraction based on either apparent unusual morphology or observed cytotoxicity in small scale extracts. Two very pale yellow compounds were isolated from cytotoxic extracts prepared from culture broths of a Fusarium sp. The first compound (A) was identified as a novel trichothecene called 4-deacetoxy-8-isobutyrylneosolaniol. The second compound (B) was identified as the 4-hydroxy derivative of A, previously only known through semisynthetic preparation. The known compound cephalochromin (C) was purified from the culture broths of two unidentified Cephalosporium-like Hyphomycetes. The identity with cephalochromin was confirmed by comparison of published NMR and circular dichroism spectroscopy. An intense yellow compound was isolated from an extract prepared from culture broths of an Alternaria sp. This compound was identified by NMR spectroscopy as a novel altersolanol called altersolanol J (D). The known compound 1-hydroxyaclacinomycin T (E) was isolated from the culture broths of a Streptomyces sp. A further five related compounds (F - J) were also isolated the culture broths. Compounds F and G, were shown by NMR spectroscopy to be stereo isomers of pyrromycin called 9-epi-pyrromycin and (7R9R1OR*)-pyrromycin respectively. The low isolated mass of compound H prevented a complete identification but was tentatively assigned by NMR spectroscopy as an N-demethyl derivative of pyrromycin. Compounds I and J were both shown by NMR spectroscopy to be novel pyrromycin derivatives called 1-hydroxyauramycin T and 1-hydroxysulfurmycin T respectively. The known compounds actinomycin V (K), actinomycin Xo (L) and actinomycin D (M) were purified from extracts of the culture broths of three Streptomyces sp. The identities of all these compounds were established by 1D and 2D NMR spectroscopy and comparison to previously reported data.