Abstract Five fungal isolates from Zea mays L. rhizosphere soil produced ethylene (C 2 H 4 ) from l -methionine. Their potential to produce C 2 H 4 was comparable to the soil isolates, Mucor hiemalis and Candida vartiovaarai but much lower than Acremonium falciforme . Investigations were made to determine if A. falciforme could utilize S -adenosylmethionine (SAM) and 1-aminocyclopropane-1-carboxylic acid (ACC), as substrates in C 2 H 4 synthesis as demonstrated in higher plants. A. falciforme grew well on ACC but no C 2 H 4 was produced, while it could not use SAM as a C source. Results indicate that the pathway of C 2 H 4 biosynthesis derived from l -methionine for A.falciforme is different from that of higher plants. Among compounds tested as substrates for C 2 H 4 production by A. falciforme , l -methionine was the best precursor. A substrate concentration ( l -methionine) of 1 mm, pH 6–7, 0.25% glucose, no N, 30°C and shaking (aeration) were optimal conditions for C 2 H 4 production by A. falciforme . The release of C 2 H 4 continued during 7 days of growth but the highest rate of synthesis was observed between 48 and 72 h. Cobalt (1 μM) slightly stimulated C 2 H 4 production, while higher concentrations were strongly inhibitory.