The OECD Screening Test biodegradabilities of ethoxylated. dodecanols rose (from 83 to max. 86.5%) and decreased (to 82% at 25degreesC in 19 days) as the average degree of ethoxylation (n) was increased (n = 1, 5 and 12, resp.). To prepare the narrow-and the broad-distributed fractions, NaOH and a coordinated Ca compound were used as catalysts, resp. The former fractions (n = 1-12) were biodegraded easier than the latter, presumably because they contained less (5 vs. 20%) high-M (around 600) fractions and their polyoxyethylene chains were less coiled.