Commercial dairy producers get frustrated by the low ratio of female to male calves born because female calves are more valuable than bull calves. The objective of this data analysis was to determine if any parameters could be identified that may be influencing the ratio of female to male calves born on the dairy operation. Data from the University of Illinois and the University of New Hampshire Dairy herds were collected and summarized for calf sex, number of services to achieve conception, and lactation number of the lactating dairy cow when she conceived. Logistical regression procedures were used to analyze the data set via version 9.4 of SAS. The data set was edited to delete those cow observations when the number of services to achieve conception (n = 6) or lactation number (n = 2) were greater than 9. These cows would typically be classified as “do not breed” and sold for harvest. The final data set contained 2,987 calvings, which consisted of 1,406 females and 1,581 males (47.1 and 52.9% for females and males, respectively). The frequency distribution of number of services to achieve conception was highest for first service and progressively declined with increasing services (52.1, 21.7, 10.8, 6.7, 4.2 and 4.7% for 1 to 6 services, respectively). The frequency distribution of calvings by lactation number was highest for 1st lactation cows becoming pregnant with their 2nd calf and declined with increasing lactation number (35.5, 28.2, 17.0, 9.6, 5.0, 2.5, 1.1. 0.1 and 0.3% for lactation number 1 to 9, respectively). Logistic stepwise regression indicated that number of services to achieve conception was significant (P < 0.02) in predicting the ratio of female to male calves. Calculation of odds ratios indicated that as the lactation number increased the likelihood of getting a bull calf decreased. These data demonstrate that increasing number of services to achieve conception and age of the cow increase the probability of getting a heifer calf. The earlier in DIM or age a cow conceives will increase the odds of the dairy producer getting a male calf.