Number of species: Approximately 200 species.
Toxins: Various toxins by different species: penicillic acid, peptide nephrotoxin, viomellein, xanthomegin, xanthocillin X, mycophenolic acid, roquefortin C & D, citrinin, penicillin, cyclopiazonic acid, isofumigaclavine A, penitrem A, decumbin, patulin, citreoviridin, griseofulvin, verruculogen, ochratoxin, chrysogine, and meleagrin.

A wide number of organisms have been placed in this genus, therefore, identification to a species is sometimes difficult. Often found in aerosol samples, it is commonly found in carpet, wallpaper, and in interior fiberglass duct insulation as well. Many species of Penicillium are common contaminants on various substrates and are known as potential mycotoxin producers.