The rheological properties of three different concentrated yoghurts (∼23% total solids, pH 4.0) and a standard yoghurt (∼16% total solids, pH 4.3) were determined during incubation and storage. The high solids yoghurts were manufactured from milks concentrated by ultrafiltration (UF) to 9% protein, by reverse osmosis (RO) to ∼6.8% protein and by direct reconstitution of full-fat milk powder to ∼6.4% protein; the standard product contained ∼4.3% protein. Development of the gel structures during incubation was monitored discontinuously using a stress-controlled oscillatory dynamic rheometer. The complex modulus (G∗) and loss tangent (tanδ) were measured as functions of amplitude (torque range 10-3–10-2 mNm at 0.25 Hz). In the RO- and direct reconstitution yoghurts, a typical pattern of gelation was observed, with the initial viscous nature of the milk being modified by rapid development of a gel structure and, finally, a ‘stationary phase’ with respect to rheological changes. However, the complex modulus (G∗) of the higher protein system (UF-milk) continued to increase with time, i.e., further development of the gel structure occurred during storage. The relative rates of gel development were dependent on protein content.