Not much. In certain episodes there may be some sexual references or content, but it is little, and no naked "adult bodyparts" are ever shown in the series.

There are alot of scenes with violent incidents, such as explosions, gunfire, and people getting killed by them. Some episodes are worse than others, but mostly, the violence is limited to undetailed killing, without much blood. When the Wraith "feed" of humans, which involves shoving their hands into the preys chest and basicly sucking the life out of them, it is obviously very painful as the humans often scream out in agony. The faces of those being fed upon are also seen shrinking together as they grow really old at an alarming rate. This can be frightening to younger audiences. And the wraith feeding of humans is a key element in the show, so it's not unusual that this is shown.

Swears and curses are limited to words like "Damn", "Crap", "Ass" and "Hell".

In some scenes people could be drinking alcohol or smoking a cigarett, but it is always responsibly, and no violence is caused by being drunk, or anything like that.

A large group of people (20-25) are seen laying dead on the ground, side by side in a mass grave, with bloody wounds on their necks. There's also a lot of fighting in that episode. In the later mentioned episodes, there are zombie-looking creatures (aliens), who are seen hunting humans. In one scene a man is standing in front of a window as it brakes and he is dragged out by dead hands as he screams. Not many of these episodes exists, and the rest of the show is not as violent as this. As before mentioned, the Wraith's (the main enemy) feeding process can be frightening to young kids.