Seventy‐four isolates of fungi includingTrichodermaspp. (18),Gliocladiumspp. (12),Coniothyrium minitans(39),Chaetomium globosum(3),Chrysosporium luteum(1), andFusariumsp. (1) were screened for ability to parasitise sclerotia ofSclerotinia sclerotiorum.Seventeen isolates killed all sclerotia after 4 weeks of incubation, with a further 15 isolates reducing sclerotial viability to less than 20%. These 32 isolates were screened in a second sclerotial parasitism test, where solid substrate ( 1 % kibbled maize:perlite colonised with antagonist) was incorporated into soil. Twenty‐four isolates significantly reduced sclerotial viability compared to the untreated control, withC. minitansConio, CH1, T5R4 2g, A69, and T5R4 2i giving the greatest reduction.C. minitansisolates showed considerable variation in their ability to parasitise sclerotia with some showing high activity but others little or no activity. Two New Zealand isolates (A69 and T5R4 2i) and two overseas isolates (CHI and Conio) were compared further. Increasing the length of the incubation period after treatment of sclerotia with C.minitansresulted in a decrease in the viability of sclerotia and an increase in the infection of sclerotia byC. minitans.This effect was significantly greater for isolates CHI and Conio compared with A69 and T5R4 2i. Incorporation of spores of the four isolates into soil (1 × 106spores/g soil) reduced sclerotial viability, with all isolates of antagonists surviving in the soil for the 2‐week duration of the experiment. Variation in the susceptibility of threeS. sclerotiorumisolates to sclerotial parasitism byC. minitansCHI and A69 was observed, withS. sclerotiorumisolate S9W1 the most susceptible and isolate S35 the least.