A fixed film spiral bioreactor containing immobilized activated sludge microorganisms has used to degrade methanol vapors. Ths effect of air flow rate and methanol feed concentration on elimination capacity has been investigated. Air flow rate & methanol feed concentration are varied in the range from 2.7 to Lmin(-1) and from 1000 & 9000 ppmv. In the concentration ranges studied, the elimination capacity increased proportionally with an increase in feed concentration. However, the elimination capacity decreased significantly at flow rate greater than 15 Lmin(-1) owing to insufficient residence time. The maximun elimination capacity observed was 183g methanol h(-1)m(-3) of reactor volume. These date are extremely useful in designing bioreactor for large scale application.