Sponges of the genus Carteriospongia have been found to contain predominantly hydrophobic scalarane derivatives, with nothing being reported concerning the more hydrophilic compounds that may be present. Carteriospongia sp. was collected in March 1993 from a depth of 8 m at Kelso Reef, the Great Barrier Reef, Australia. The dry tissue was exhaustively extracted with dichloromethane and methanol, and the water-soluble part of the methanol extract was fractionated by RP (C18) vacuum liquid chromatography followed by RP (C18) HPLC to afford uracil, thymine, thymidine, 2'-deoxyuridine, 2'-deoxyinosine, (—)-2-hydroxybutanoic acid, (—)-3-hydroxypentanoic acid (a new natural product), and 2 amino-2-methyl-4-pentanone. All structures were deduced on the basis of spectroscopic data (predominantly 1H- and 13C-NMR, ElMS and GC-EIMS). Compound 2 amino-2-methyl-4-pentanone was suggested to be a natural product as acetone was never used in any phase of the work. Western juniper (Juniperus occidentalis Hook, Cupressaceae) heartwood essential oil, which has shown acaricidal activity against both nymphs and larvae of Ixodes scapularis (a vector of Lyme disease), was further investigated. The C14 sesquiterpene (+)-dihydromayurone was isolated and identified by spectrometric techniques, representing the first isolation of (+)-dihydromayurone as a natural product.