Button disappear on click

I have two buttons and wanted to get one disappear when someone clicks on the other
For btn1:
on(release){
this._visible=0; //this doesnt works
btn2._visible=true;
// btn2._visible=false;
// trace(“From first button”);
// btn1._visible=0; //this works
}

btn2:
on(release)
{
this._visible=0; //this doesnt works
//btn2._visible=false; //it works
btn1._visible=true;
// trace(“From second button”);

}

But it doesnt seems to work although btn._visible works
Any idea why?