Bankia setacea prefer to attack upper horizontal wooden surfaces, whereas Limnoria spp. prefer the lower surfaces. Attack by B. setacea is heaviest at the mudline and decreases almost linearly with decreasing depth. Limnorial attack is heaviest in the intertidal zone, then is relatively constant with increasing depth. Statistical studies showed non-normal distribution of populations, with limited replicability, particularly for low Bankia counts. The desirable period of immersion is greater than 2 weeks, but in most commercial monitoring situations is limited to 1 month. Attack data on immersion specimens are compared with those on floating logs. On the basis of the results, procedures have been designed for monitoring attack in the commercial evaluation of impregnants, as well as for estimating population densities.