What is considered proper? Sportshirt, sportcoat, or suit and tie?

Hi Boz: I think any of your above choices would be fine. We didn't go to the Estates Theatre, but did see an opera at the National Theatre last May. It seemed to me most dressed up a bit, but there were also people in jeans and more casual attire. I wore a long skirt and dressy sweater and my husband wore a suit, dress shirt and tie, but that's how we would dress here at home for a similar performance, not necesarily what you should do.

A suit and tie would be considered proper. A sportcoat would work.

A sportshirt (by which I assume you mean some kind of knit shirt as for tennis or rugby or those things with logos on the pocket and short sleeves) is not proper for the opera. YOu will probably not be kicked out, but it is not appropriate.

We saw Don Giovanni here in July. Most of the men wore slacks and a sportshirt. I only remember seeing one young couple that was really dressed up. Most of the ladies wore skirts. Of course it was hot there in July so you might like to consider a sportcoat if you are going soon. Also, I would think you could wear a suit and tie if you desire but most of the people there were tourists and while all looked nice most were not overly dressed up.

Estates tends to have almost all tourists in the audience during the summer, which means "neat casual" will be the norm. The place IS NOT air-conditioned, as advertised. (At least not in the main hall!). During the main season, I would dress up a bit more. Czechs attend the opera DRESSED. I've seen heads turn at ladies who are wearing their finest. Almost like a fashion show in the audience. As long as you arrive neatly dressed & have good manners, you should be fine. Enjoy! PS : what are you seeing there?