Neutral sugar compositions of materials released from isolated mycelial walls of race 1 and race 2 of Fusarium oxysporum f. sp. lycopersici and Fusarium oxysporum f. sp. cubense were similar (5% ribose, 52% mannose, 28% galactose, 15% glucose). High molecular weight glucans were isolated by ion-exchange chromatography from the cell wall extracts of each of the Fusarium isolates. The linear chain linkage structure of the Fusarium glucans was predominantly 1—3 and 1—6. That of the Colletotrichum lindemuthianum glucans was 1—3 and 1—4. These Fusarium glucans were nearly as effective as glucans from Colletotrichum species at eliciting browning and phytoalexin production in green bean cotyledons. Tomato fruit and stem tissue showed browning and phytoalexin production when exposed to F. oxysporum f. sp. cubense spores. These symptoms did not develop upon treatment of tomato tissues with the Fusarium or Colletotrichum glucans that had elicitor activity in green bean.