If you purchased them through a hatchery, most hatcheries tell you to expect a 90% accuracy with sexing. Depending on how many you ordered, you could get a roo or two in the bunch, or you may be lucky enough to have just all pullets.
If you purchased through a feed store, I hear they are...
A topic that comes alot around here! With Straight Run chicks, you are forced to wait it out. Sometimes you'll know in a couple weeks, sometimes not for a couple months, or until the boys start crowing! With mine, it was roughly 5 weeks until I was fairly certain who was who.
Things to watch...