9108 Background: Fatigue can be measured with different validated assessment instruments in symptom management trials. Methods: Between 2004-2009, the Wake Forest CCOP Research Base protocol 97202 randomized 236 women receiving adjuvant chemotherapy for newly diagnosed breast cancer to Coenzyme Q10 supplementation vs placebo. The primary endpoint was change in self-reported fatigue. Patients (pt) were assessed at baseline, 8, 16, and 24 weeks (wk) with 3 instruments: 1) Profile of Mood States – Fatigue (POMS; 7 questions; scored 0-4); 2) Functional Assessment of Cancer Treatment – Fatigue (FACIT; 13 questions; scored 0-4); and 3) Visual Analog Scale (VAS; one scale; scored 0-10). For comparison, each instrument was rescaled from 0 to 100; higher numbers indicate worse fatigue. Results: CoQ10 did not significantly affect fatigue (Lesser G et al, ASCO Proc., 2010). All 3 measures demonstrated an increase in fatigue after chemotherapy initiation at 8 & 16 wks with trend towards baseline levels at 24 wks. The fatigue measures were highly correlated: r ≥ 0.8 for all pairwise associations at all times. However, their scores varied. The Table shows mean rescaled scores for pt below/above the median fatigue level, calculated by taking mean of the three scores averaged across the four time periods. In general, POMS tended to give the lowest and VAS the highest scores, but differences between POMS and FACIT and FACIT and VAS depended on mean fatigue level. For pt experiencing lower (<median) fatigue, FACIT and VAS scores were similar, while POMS scores were significantly lower. For higher (>median) fatigue, POMS and FACIT scores were similar, while VAS was significantly higher. Conclusions: While POMS, FACIT, and VAS scores were highly correlated, their scale scores varied depending on the level of fatigue experienced by the pt. Fatigue assessment methods in clinical trials should be selected carefully as they do not always give equivalent results. Supported by NCI/DCP grant U10 CA81851. [Table: see text]