Samples of curd and cheese, taken throughout cheese-making with milks concentrated to different extents, were examined by light microscopy and by scanning and transmission electron microscopy. The mature cheeses were analysed for textural parameters by instrumental and sensory means. The protein was packed in larger, more compact areas and the fat was more segregated in the curds and cheeses from the more concentrated milks. The protein network increased in coarseness in proportion to the concentration factor of the milk, the relative differences being the same throughout cheese-making into the mature cheese. Thus, the basic structure of the protein network was laid down during the curd firming process and was not fundamentally altered later in cheese-making. The fat/protein interfaeial area in the cheese and the changes in structure during maturation decreased as the concentration factor of the milk increased. The instrumental firmness, cohesiveness and force and compression required to cause fracture, and the sensory firmness, crumbliness, granularity and dryness of the cheese all increased as the concentration factor of the milk increased. The adhesiveness declined and there was little change in elasticity, with increase in milk concentration factor. The textural differences were related to the smaller fat content, lower level of proteolysis, stronger links in the protein matrix and reduced capacity of the fat and protein phases to move relative to each other in the cheeses from the more concentrated milks.