This paper deals with the study of the sugar cane borer, its relation with infestation and its damage in the cana crop and in the sugar factory. Diatraea saccharalis Fabr.. 1794 Crambidae, Lepidoptera) was the only species found. The following varieties of sugar cane were studied: Co 419, CB 41-76 and CB 40-69, in the regions of Piracicaba, Araras, Santa Bárbara d'Oeste and Araraquara, State of São Paulo, Brazil. The work was carried out taking, at random, stalks of the mentioned varieties; these stalks were divided into three pieces: basal, middle and apical. The total number of joints of each stalks and after sectioning the stalks longitudinally, the number of infested joints, were counted, to determine the intensity of infestation. To check the borer damage in the cana and in the sugar factory borer-free cane and infested cane was collected, weighted and its content of sucrose per cent cane determined. The average infestation intensity of those locations was 15,8% for variety Co 419, distributed as follows: 6,1% in the basal, 6.7% in the middle and 3,0% in the apical piece; 21,5% for variety CB 41-76, respectively, 6,9, 9,7 and 4,9% for the same pieces; and 28,8% for variety CB 40-69, respectively, 8,4, 13,8 and 6,6%. The ground average is 22,2%. The average loss in the sugar cane weight was 4,4, 3,2 and 6,7% respectively, for the varieties Co 419, CB 41-76 and CB 40-69. The ground average is 4,8%. The average loss in sucrose per cent cane for the varieties Co 419, CB 41-76 and CB 40-69 is, respectively, 1,6, 4,1 and 6,7%. The ground average is 4,1%. This damage represents a loss of 106.075 tons of sugar cane and 133.166 sugar bags (of 60 kg each) in the 5 factories sudied, in the 1960/61 harvest. Both data are in relation with the average infestation intensity of 22,2%.