The structures and properties of monolayers and Langmuir–Blodgett films of conducting oligo- and polythiophenes are analysed. The published data on the influence of the number, size, and composition of substituents in polythiophene molecules and of the pattern of their distribution along the chain on the monolayer stability and Langmuir–Blodgett film quality are generalised. Considerable attention is given to the description of the behaviour of mixed monolayers and Langmuir–Blodgett films composed of polythiophenes and various amphiphilic compounds. The effective conjugation lengths of polymer chains and conductivities of polythiophenes in Langmuir–Blodgett films and cast films are compared. Examples of the use of Langmuir–Blodgett films for scientific and technological purposes are given. The bibliography includes 100 references.