Abstract: A thickened organic solvent based system, particularly an aliphatic hydrocarbon-based liquid composition, such as an ink, the polymeric thickener therefor, a method of making the thickener by emulsion polymerization, and methods of using the thickener are disclosed. The thickener is an addition polymer of ethylenically unsaturated (A) hydrophobic monomers being within the hydrogen bonding class of from moderate to poor and (B) hydrophilic monomers being in the strong hydrogen bonding class in a weight ratio of hydrophobic: hydrophilic monomer between about 99.1:0.1 and 90:10, at least about 60% of the hydrophobic monomer(s) (A) are those whose homopolymers have a solubility parameter of .ltoreq.8.8, any other hydrophobic monomer(s) being such as to not destroy the organic solvent solubility of the polymer. The hydrophilic monomer(s) (B) preferably comprise at least a predominant proportion of monomers containing at least one of a carboxylic acid group and a sulfonic acid group.