An aerosol generating substrate comprising an aerosol generating material. The aerosol generating material comprises an amorphous solid which comprises 1-60 wt % of a gelling agent, 5-80 wt % of an aerosol generating agent and optionally 0.1-60 wt % of at least one active substance and/or flavorant (dry weight basis). The amorphous solid comprises from about 1 wt % to about 15 wt % water, calculated on a wet weight basis.