Sub-micron and micron-size stable particles of water-insoluble or poorly soluble drugs or other industrially useful insoluble compounds suspended in an aqueous medium containing at least one surface modifier are prepared by selecting the surface modifier or modifiers such that the hydrophile-lipophile balance (HLB) of the composition, defined as formula (I): is between 4 and 9. This provides a reliable HLB-based selection criteria for selecting the type and amount of surface modifiers used to obtain sub-micron size stable suspensions.