Conidia of Trichoderma harzianum and T. pseudokoningii (Rifai) were formulated to make alginate pellets with or without 10% cellulose as a food-base material. The formulations were compared for their ability for survival and proliferation of Trichoderma spp. in clay-loamy soil (50% moisture content) with allyl alcohol fumigation (0.05, 0.1 and 0.2 ml/1,000 ml space). Trichoderma medium E (TME) containing 100 microg/ml pentachloronitrobenzene (PCNB) was valuable for isolation and counting of Trichoderma spp. from the tested soil than the Glucose-Czapek's agar medium containing 1:15,000 Rose-bengal. The promotive effect of Trichoderma by different doses of allyl alcohol fumigation still enhanced after two-month incubation period. Conidia entrapped in alginate with or without cellulose and introduced into the soil survived better than conidia added directly to the same soil after three months incubation period. Sterile soil provided a more favorable environment for the proliferation and survival of immobilized conidia than the non-sterile soil, and the addition of 10% cellulose increased the survival of the entrapped conidia more than those prepared without cellulose. Soil fumigation inhibited the occurrence of other fungal species; however, inoculation of the soil with alginate immobilized conidia or conidial suspension had such inhibitory effect but in a less extent.