In the course of studies carried out in this laboratory into the neurological disorder of sheep and cattle known as ryegrass staggers, P. paxilli has been isolated from the feces of cattle in Victoria and from soil from pastures on which an outbreak of ryegrass staggers occurred in South Australia. Both of these isolates of P. paxilli produced substantial quantities of verruculogen (1) as the only detected tremorgen. This result is at variance with the published isolation of the much less potent (3) and structurally dissimilar (5) tremorgen paxilline (2) from P. paxilli and prompted a direct comparison with the North American isolate (3). When cultured in quantity under conditions identical with those used to culture our isolates of P. paxilli, this isolate produced paxilline (2), as reported (3), and no detectable verruculogen (1), thus confirming a difference in secondary chemistry of the North American and Australian isolates.