Ectotrophic forest tree species planted in soils deficient in ectomycorrhizal (ECM) fungi have been shown to benefit greatly from ECM inoculation. A major goal of ECM inoculation is to use efficient technique to minimize the amount of inoculum needed to obtain the required extent of ectomycorrhizae on roots of seedlings. This chapter is a brief review of inoculum types and procedures of inoculum preparation and application developed in ECM research. The use of natural inocula, such as soil, litter, humus, ECM seedlings, or excised ectomycorrhizae satisfied the assumption that some ectomycorrhizae on roots are better than none. Spores and vegetative (mycelial) inoculum represent a higher level of ECM inoculum which enables to form specific ECM associations. Vegetative inoculum can be produced in the form of pure mycelial culture, various substrates permeated by mycelium or mycelium incorporated in beads. In ectomycorrhiza synthesis in aseptic conditions, fungi are introduced into synthesis vessels as either agar culture transfers or liquid cultures. In operational conditions, vegetative inoculum is mostly mixed, banded, layered, or poured into soil or substrate. There are a lot of ways of spore application, e.g., mixing spores with substrate, irrigation of substrate by spore water suspension or injection of suspension to root zone of plants. Inoculum can be applied before, when seeds are sown or seedlings planted, and after seedling emergence. A list of the literature cited in this chapter may serve as a link to other references and detailed information in this field of ECM research.