Oidiophores with uninucleate oidia are produced on the aerial mycelium of Coprinus cinereus and occasionally also on the submerged mycelium. Oidiophore development starts with the formation of a stem cell and proceeds with stem cell elongation, followed by the formation of oidial hyphae at the tip of the stem cell and subsequent release of matured oidia. However, analysis of more than 20 different C. cinereus strains revealed that oidiophore formation is a flexible process. Based on morphological variations, we defined four main types of oidiophores. Types 1 and 2 oidiophores produced oidia at the tip(s) of simple (type 1) or branched stems (type 2). Types 3 and 4 oidiophores were characterized by the absence of stem cell elongation (type 3) or stem cell formation (type 4). All strains examined produced types 1 and 2 oidiophores and some produced also types 3 and 4 oidiophores but the frequency of the different oidiophore types varied strongly from strain to strain.