Sir,- The presence of neurotoxins, two of which were named lolitrem A and lolitrem B, in perennial ryegrass associated with outbreaks of ryegrass staggers (RGS) in sheep was reported in 1981.(6) Lolitrems are lipid-soluble compounds which induce protracted tremors when dosed i.p. to mice and which have also been found in a number of lines of ryegrass seed.(4)Lolitrem-containing seed, fed to sheep, produced symptoms similar to those of RGS, whereas no symptoms were seen in sheep fed lolitrem-free seed.(04) The reversability of the induced neurotoxicity, a well-known feature of RGS(05) (07) was observed in these experiments.