The aim was to study seasonal influence on the chemical composition, somatic cell count (SCC) and total bacteria count (TBC) in bulk tank milk in the Brazilian Northeast. The data analyzed was obtained from 116.989 samples of bulk tank milk collected from industries that have an account at the Federal Inspection Service (FIS). The samples were separated into three periods (I,II,III), according to application of IN-51. PROC GLM was used to study the comparison of means by Duncan's test. The fat varied more, with an average of 3.66%, protein and lactose had an amplitude of 0.04% between periods, and an average of 3.16 and 4.41%, respectively. Higher values of SCC were observed in the months from May to July (594.33 to 625.28 thousand cells/mL), while in TBC the largest values occurred in May and June (1308.54 and 1333.83 CFU/mL). Significant differences in milk components between states were observed, especially with regard to hygienic quality. The chemical composition, SCC and TBC were influenced between periods and months of the year.