Entomopathogenic nematodes are widely used as biological insecticides for agricultural and horticultural pests. In the vast majority of cases, commercial products contain nematodes partially dehydrated on to inert solid carriers. Nematode survival in these products is generally poor, they are difficult to handle and are not suitable for use with all nematode species. We have developed a non-viscous, non-adhesive and non-toxic liquid formulation for nematode storage and transport based on neutral density colloidal silica suspensions. Survival and virulence of nematodes stored in this formulation without aeration was superior to nematodes stored in aerated quarter strength Ringer's solution.