I've got brown streaks on my ceiling. Is it a leak, and what should I do first?

Brown streaks on a ceiling usually point to a water leak. First, gently press a paper towel to the stain to see if it's wet. If damp, immediately look directly above – check the attic for roof leaks, or the floor above for plumbing issues like a leaky pipe, toilet, or shower pan. Fixing the source quickly prevents mold and structural damage. If the streaks are dry and follow framing lines, it might be 'ghosting' from temperature differences, where dust settles on colder spots; this often indicates an insulation issue. For an active plumbing leak, call a licensed plumber. For a roof leak, a roofer.