For what it's worth, everyone in my cancer support group (there are about 10 of us who continue to meet monthly for lunch) are experiencing fatigue. We're all on either Arimidex or Letrozole, we all were diagnosed last summer, have had varying diagnoses and treatments, are different ages, some work and others don't, we're all frustrated that we're not as quick mentally as we were a year ago... and by ap. 4 p.m., we're exhausted. Those of us who must prepare dinner for others find that the evening is a total loss as our brains simply stop working by then. Considering what we've been through (and some are still receiving treatments), it doesn't surprise us. Our oncologists tell us this reaction is to be expected... regrettably.