Resorption of conceptuses was identified in 6 of 20 bitches examined daily from 15 to 35 d after the estimated pre-ovulatory LH surge. One or more conceptuses were resorbed in each bitch but there was continuation of the remaining pregnancy to term. This paper details the ultrasonographic embryological features of normal and resorbing conceptuses. Impending resorption may be predicted by detecting a delay in the time of development of a specific embryological feature or measuring a slow growth rate. Interestingly, there were greater number of conceptuses initially identified in bitches that subsequently resorbed than in those which did not.