Forty species of fungi, representing a range of ecological and taxonomic groups, were tested for their ability to grow on agar media amended with lithium chloride (LiCl) at 1.5, 3 and 6 g l(-1). Species of Trichoderma varied considerably in their sensitivity to LiCl; at one week on 6 g l(-1) LiCl medium, the growth of seven species of Trichoderma was considerably inhibited; however, by three weeks at this level, four of the species tested were able to attain > or =30% of control growth. Of the seven species tested, an isolate of T. viride was the most sensitive to LiCl in agar. Eleven other imperfect fungi also showed a range of ability to grow on agar amended with LiCl, from total inhibition to complete lack of inhibition. Six ascomycete fungi were greatly inhibited by LiCl at all levels; however, an isolate of Chaetomium globosum was highly tolerant of LiCl. Seven basidiomycete wood-decay fungi were quite sensitive to LiCl in agar, showing total to nearly total inhibition even at the lowest level; however, after three weeks, an isolate of Postia placenta was nearly uninhibited except at 6 g l(-1). Five ectomycorrhizal basidiomycete fungi were totally inhibited by all levels of LiCl; however, one ectomycorrhizal imperfect fungus (Cenococcum graniforme) was able to grow at 3 g l(-1) and was uninhibited at 1.5 g l(-1). Four zygomycete fungus isolates were nearly unaffected in their growth by all levels of LiCl.