The objective of the present study was to determine the diameter, area, circumference, and blood flow of the corpus luteum (CL) using transrectal ultrasonography in female alpacas with and without the presence of an embryo on Day 9 post-mating, the time of maternal recognition of pregnancy (MRP). For this purpose, 12 female alpacas with follicles ≥ 7 mm were mated with fertile males and treated with 0.0084 mg of buserelin acetate (Day 0). After that, the females were randomly classified into 2 groups (6 animals/group): (1) CL with embryo and (2) CL without embryo (embryo removed from the uterine horn on Day 9). In both groups, transrectal ultrasonography was performed on Day 2 to determine ovulation, and on Days 5, 7, 9, 11, and 13 to evaluate the CL. The data were analysed using repeated measures ANOVA. The diameter (mm), total area (mm