MILK production records for an Egyptian buffalo herd were collected in the period from 1970 to 1985. Data on 2739 lactation records including 696 buffalo cows (Paternal half-sisters) representing 67 sires were used to estimate the genetic and phenotypic variations and covariations of lactation period (LP) and yield of milk recorded on 90 days (90DY), 180 days (180DY), 305 days (305DY) and total lactation cro. Averages of 90DY, 180 DY, 305DY, TY and LP were 601, 999, 1361, 1558 kg and 288 days, respectively. Parity effects were highly significant ( P < 0.001) for all milk yield traits. All productive tratis increased with parity order till reaching the peak and declined thereafter, except TY and LP increased linearly as order of lactation advanced. Season of calving affected (P