Total of 510 lactation records, representing five successive parities, were collected on 102 cows (20 Ankole and 82 Sahiwal x Ankole crosses)  to study the effect of grading up Ankole cattle of Burundi with Sahiwal breed on both   total milk yield and lactation length.             Generally, the increase of Sahiwal blood in the Ankole cattle of Burundi by up-grading increased both total milk yield per lactation and lactation length.               Genotype had significant effect (P<0.001) on both milk yield and lactation length. However, parity only significantly affected (P<0.001) total milk yield per lactation. The 75, 87.5 and 93.75% Sahiwal cows yielded more milk per lactation than did 50% Sahiwal cows. However, for about the same length of lactation, the difference in total milk yield between 75 and 87.5% Sahiwal cows was not significant. The Ankole cows yielded, compared with the crossbred cows, less milk per lactation in shorter lactation.                  For all crossbred cows, the percentage of improvement in total milk production attained its maximum at the 5^th parity (ranged from 156.1 to 281.4%).