One of the most telling clues that the operation is an abortion comes toward the end when the man says,
"You've got to realize that I don't want you to do it if you don't want to. I'm perfectly willing to go through with it [the pregnancy] if it means anything to you."
And later he says,
"But I don't want anybody but you. I don't want any one else. And I know it's perfectly simple."
The setting itself also gives clues that the couple is talking about a decision between productivity and barreness. On one side of the train station are fields of grain,trees, and water; on the other side, the valley is dry and barren. It is the dry side of the valley that the girl contemplates in the end, symbolizing the couple's decision to have the abortion so that things could be like they were before, as the man so claims.
Contextual clues in the conversation between the two main characters in Hemingway's story "Hills Like White Elephants," lead us to believe that the operation the American man is referring to is an abortion for Jig, the female character. As they are sitting in the shade outside a bar waiting for the train, the man is trying to convince her that it is "not really an operation." He also tries to reassure her that things will be just as they were before once she returns from having the procedure. The more he says, the more upset she gets, until finally the train arrives, and it is too late to turn back. Neither of them ever say the word that will make the situation real; instead they choose to dance around it, having drinks and trying to make small talk, but it is clear that he is fairly desperate to talk her into it, and that she knows that she doesn't really have an alternative.