Timing of artificial insemination (AI) in marsupials is critical because fertilization must occur before mucin coats the oocyte during passage through the oviduct. In this study, timing and the site of insemination were examined to develop AI in the tammar wallaby (Macropus eugenii). Birth and postpartum (p.p.) estrus was synchronized in 46 females. Epididymal spermatozoa (n = 4) or semen collected by electroejaculation (n = 42) were inseminated early (4-21 h p.p.) into the urogenital sinus (n = 7), the anterior vaginal culs de sac (n = 7), the uterus by transcervical catheter (n = 5), or the uterus by injection (intrauterine artificial insemination, IUAI) (n = 5). A further 16 females were inseminated late (19-48 h p.p.) by IUAI. All females were monitored for birth. A third group of six females was inseminated late (21-54 h p.p.) by IUAI and 0.4-6.6 h later, sperm had reached the oviduct in all animals. In total, an oocyte to which spermatozoa were attached was recovered and two young were born after IUAI using epididymal (n = 1) or electroejaculated (n = 2) spermatozoa, but no young resulted from insemination at other sites. Two females were successfully inseminated at 43 and 47 h p.p., later than most other animals, and the third was inseminated much earlier (18 h p.p.) but with highly motile spermatozoa. These young represent the first macropodids born by AI and the first marsupials conceived using epididymal spermatozoa.