The hydrophilicity of surface-active crown compounds and their change upon the addition of electrolytes were investigated by measuring the phase-inversion temperature (PIT), the phenol index, and the cloud point. Sodium chloride and potassium chloride were observed to raise the hydrophilicity of 15-crowns and 18-crowns respectively, in contrast with their lowering effect on the hydrophilicity of usual poly(oxyethylene)-type nonionics. The effective HLBs of dodecyl crown ethers, estimated from both the PIT and the phenol index, were compared with those of poly(oxyethylene) dodecyl ethers, and the hydrophilicity of the crown rings were discussed in conjunction with that of the poly(oxyethylene) chain.