The role of ethylene during in vitro maturation of Nicotiana tabacum pollen from the mld-binucleate (MB) stage was analysed by the addition of aminooxyacetic acid (AOA), aminoethoxyvinylglycine (AVG), CoCl2 and AgNO3 to the maturation medium (AMGLu). An increase in ethylene production was obtained in both isolated pollen and pollen surrounded by sporophytic tissue during in situ maturation. in vitro maturation of pollen was inhibited by AOA and AVG; ACC and ethrel were able to overcome this inhibitory effect. Cyclohexylamine (CHA) reverted the inhibition provoked by both Ag+ and Co2+ The results reported in this paper indicate that ethylene is one of the factors implicated in in vitro maturation of MB pollen of Nicotiana tabacum.