Fifty-two fungal isolates obtained from seawater were screened for anti-nematode activity. One isolate, an Acremonium sp., exhibited the highest activity against the pinewood nematode, Bursaphelenchus xylophilus. When it was grown at pH 7.0 and 24-26 A degrees C, nematicidal metabolites were produced. These were heat-stable, water-soluble molecules with MWs < 6 kDa. Nematicidal activity was highest at neutral pH.