Records of high grade or purebred Holsteins in 62 herds on DHIA recording in Puerto Rico were used to determine phenotypic correlations of lactation length, days dry prior to lactation, days open during lactation, and interval from previous parturition (calving interval) to lactation, milk and fat yields, and fat percent. Both milk and fat yields had a significant (P < .05) positive phenotypic correlation with lactation length, calving interval, and days open (0.178 to 0.658), hut fat percent had a low relation to these traits (-0.023 to +0.014). Lactation length, dry period, days open, and calving interval were regressed on milk yield, fat yield, and fat percent. The combined contribution of these variables to variation in milk yield was 44.4%. Days open, days dry, and calving interval accounted for only 13.4% of the variation in milk yield. Days dry and days open together accounted for 9.6% of the variation, and days dry, plus calving interval, made up 6.0%, of the variation. The values for fat yield were slightly lower but followed a similar pattern as for milk yield. The four variables combined contributed only 0.23% to the variance in fat percent. Total milk yield and fat yield were inf1uenced by lactation length, calving interval, and days dry in descending order of magnitude. Days open had comparatively little influence on either milk or fat yields. Length of dry period influenced fat percent more than any other variable but to little extent. Since the majority of the variation in milk and fat yields attributed to the four variables was due to lactation length, it appears that in Puerto Rico selection with emphasis on lactation yields is unlikely to decrease fertility.