Basidiomycetes are characterised primarily by the sexual spores (basidiospores) being produced on a cell called a basidium, usually in fours. Many but not all have septal structures called a clamp connection during most of the life cycle. No other group of fungi has these.

There are about 25,000 species in this division including the more familiar types of fungi whose fruiting bodies are popularly known as mushrooms and toadstools. A number of these are edible but also are included many which are toxic or hallucinogenic. This group also contains those that decay wood or attack living trees, others, which rot down forest litter. Plus the class of fungi known as rusts and smuts.

Basidiomycete have many features in common with the Ascomycetes; mycelia with chitinous cell walls that are regularly septate, cell division often accomplished by clamp formation, and the presence of an extended dikaryon stage. This means that the two nuclei brought together in mating do not fuse in the thallus of the fungus, but instead exist side-by-side in each cell.

Basidium is the cell in which karyogamy (nuclear fusion) and meiosis occur, and on which haploid basidiospores are formed. The basidium produce four basidiospores, borne on the tips of little prongs which project from the apex, and which are called sterigmata. Conidia are produced if an asexual stage is present.

Millions of these are packed together in the hyrneniurn, which covers the exposed or enclosed surfaces of the sporocarp, which are quite variable in form. These are then discharged a short distance into the space between the gills, tubes, or teeth, of the fungi, subsequently falling the short distance out of the cap, to be carried away on air currents.

Basidiomycetes are divided into four classes depending on the form of their basidium. The Teliomycetes and Urediniomycetes are presently not covered here, as they do not produce a basidiocarp.

Class: Hymenomycetes
Class: Urediniomycetes

Class: Teliomycetes

In this class the fruiting surface, or hymenium is external

Subclass: Holobasidiomycetidae
(Homobasidiomycete Fungi)(Substantial mushrooms)
This subclass has exposed spore surface such as pores or gills, from which each basidiospore in turn is actively shot away. The class contains those fungi that are coincided to be 'mushrooms', which have a stalk, and a fleshy cap. The other members are those referred to as 'shelf fungi', which lack a stalk, and grow directly from wood.

Order: Agaricales

Family: Agaricaceae
Family: Bolbitiaceae
Family: Clavariaceae
Family: Coprinaceae
Family: Cortinariaceae
Family: Crepidotaceae
Family: Entolomataceae
Family: Hydnangiaceae
Family: Marasmiaceae
Family: Pleurotaceae
Family: Pluteaceae
Family: Schizophyllaceae
Family: Strophariaceae
Family: Tricholomataceae
Family: Tubariaceae

Order: Boletales
A distinguishing feature of this family is the presence of pores in place of gills on the fruiting bodies. Many of the boletes are edible

Family: Boletaceae
Family: Boletinellaceae
Family: Calostomataceae
Family: Suillaceae
Family: Paxillaceae
Family: Rhizopogonaceae
Family: Sclerodermataceae

Order: Cantharellales

Family: Cantharellaceae
Family: Clavulinaceae
Family: Hydnaceae

Order: Dacrymycetale

Family: Dacrymyceaceae

Order: Gomphales

Family: Gomphaceae
Family: Hysterangiaceae
Family: Phallaceae

Order: Hymenochaetales

Family: Hymenochaetaceae

Order: Polyporales

Family: Atheliaceae
Family: Ganodermataceae
Family: Gloeophyllaceae
Family: Hapalopilaceae
Family: Polyporaceae
Family: Steccherinaceae

Order: Russulales

Family: Auriscalpiaceae
Family: Corticiaceae
Family: Hericiaceae
Family: Meruliaceae
Family: Russulaceae
Family: Stereaceae

Order: Thelephorales

Family: Bankeraceae
Family: Thelephoraceae

Subclass: Phragmobasidiomycetida (jelly fungi)
(Heterobasidiomycete Fungi)
Basidia are usually septate at maturity (deeply divided), spores germinate repetitively or by budding or deeply lobed basidia that are variable in shape. Though they commonly have only four-celled basidia.

Order: Auriculariales
Auricularia has transversely septate basidia.

Family: Auriculariace
Family: Hyaloriaceae

Order: Tremellales
Tremella have cruciate septate basidia

Family: Exidiaceae
Family: Tremellaceae
Family: Tremellodendropsidaceae

Class: Teliomycetes and Urediniomycetes (Rust and Smuts)
In these two orders, not presented here, a basidiocarp is not formed, karyogamy occurs in a thick-walled resting spore (teliospore), and meiosis occurs upon germination of teliospore. These orders are sometimes put in a separate class, the Teliomycetes.

Uredinales are highly specialised parasites of higher plants with life cycles typically having up to five spore stages and two alternating hosts. The rusts cause many serious diseases of economically important hosts, including trees. They also have perhaps the most complex and perplexing life cycles, and variations on those cycles, of any group of organisms