All Lights Out

Kitchen lights are on a three-way switch. All lights plus an adjoining outlet are out.

How best to check the circuit breaker?

Other than a break in the line, could anything else cause this problem? Could the three-way switch (replaced about three years ago) be bad?

Thx…

 

I don't recommend checking the breaker except as a last resort. Breakers are probably replaced ten times as often as they really go bad, and checking them is dangerous. If the breaker was bad, then everything on the circuit would be out, not just one set of lights. Is everything on this circuit out? You can test by shutting off the breaker and seeing if anything else (such as the dining room light) stops working.

Switches do go bad, much more often than breakers.

Testing with a multimeter can see if your switches are okay.

You should also consider a tripped GFCI. Lighting is not often on a GFCI but since you mentioned that a receptacle was out too, this possibility is more significant.

Testing of a breaker is done with the panel cover off by testing with a voltmeter between the screw on the breaker and the ground bar. If you do anything wrong, however, this can easily kill you. So be sure you know what you're doing.

 

If this is a kitchen outlet it should not be on the same circuit as the lights.
When I built my house I had a batch of 10 bad 3 ways.