Abstract Several different types of preparation from leaf rust-infected leaves were applied to uninfected wheat leaves in two bioassays. One bioassay used intact leaves and symptom formation visible to the unaided eye. The other used exposed mesophylls on leaf segments which were stained and examined by optical microscopy. The first bioassay revealed previously observed elicitation that was not specific for resistance genes, and the second suggested the presence of resistance-gene specific elicitors. The second bioassay was used with extracts from leaves infected with an avirulent pathotype with respect to Lr9 and avirulent or virulent pathotypes with respect to Lr28 and using wheats differing in the presence or absence of the Lr9 or Lr28 alleles for resistance. The results indicated the presence of elicitors specific for putative Avr9/Lr9 and Avr28/Lr28 interactions among other elicitors in the extracts. Preliminary tests showed that the specific elicitors were precipitated by ammonium sulphate.