A plasma progesterone profile obtained from three consecutive blood samples with an interval of 7 days was evaluated for usefulness as the basis for the diagnosis and treatment of anestrous gilts and sows. Four reproductive statuses were categorized based on the plasma progesterone levels and pathological examination of the reproductive organs from 25 gilts and 12 sows with anestrus. Category 1: fluctuating (at least one sample <2.5 ng/ml and one >10 ng/ml) with normal ovary; Category 2: sustained low (<2.5 ng/ml) with inactive ovary; Category 3: persistent high (>5 ng/ml) with normal sized or cystic corpora lutea; and Category 4: animals not included in the categories mentioned, such as pigs with luteinized cysts and follicular cysts. Using the plasma progesterone profiles and this categorization, the reproductive status of 54 gilts and 38 sows with anestrus was predicted. Hormonal treatments were performed with moderate to high success. Results from this study indicate that plasma progesterone profiles can be useful for the determination of estrus status, for the diagnosis of the causes of anestrus, and for the prediction of the next estrus for an appropriate hormonal treatment in anestrous gilts and sows.