Abstract This presentation will provide an introduction into internationally and nationally regulated biofouling issues. The risk for spread of invasive aquatic species (IAS) via fouling from ship's hulls / other under water structures or ballast water is being focused upon more and more. IMO issued guidelines in MEPC.207(62) for the control and management of ships' biofouling to minimize the transfer of invasive aquatic species (IAS). The U.S. Coast Guard requires a Biofouling Management Plan be incorporated into, or referenced in, the Ballast Water Management Plan. California is planning to regulate biofouling on ships. Adding to this IAS issue the resistance attributed to biofouling and hull roughness are other important aspects to consider for improving the energy efficiency of a ship's operation and reducing CO2 emissions, which has been reflected in the IMO Marine Environment Protection Committee (MEPC.213(63)) recommendation for a ship energy efficiency management plan (SEEMP). Considering the above recommendations and requirements, ABS is developing Biofouling Guidance Notes and a Biofouling Management Plan Advisory to assist the shipping industry in dealing with these issues and in complying with the related requirements. ABS Nautical Systems also provides solutions that assist owners and operators in capturing data for demonstrating SEEMP compliance. Introduction The issue of hull biofouling has been of concern since floating vessels were first put into the water. In the 1900's many scientists studied the effect of biofouling on ships. Kempf reported in 1937 with an 85% increase in resistance of the ship. In the past few decades of research from R. Townsin, Goeff Swain, M. P. Schultz, and many others on the biofouling effect on ships, have provided enlightening data concerning roughness and bio-fouling contribution to total hull resistance. Studies by Townsin et al have provided the industry with a scientific understanding of the relationship between hull roughness and resistance. When this relationship is applied in a simplified manner to various types of ships it provides us with good " approximate" values. Because increased resistance is so significant in accounting for the margin of error for each specific ship, such an approximation provides good guidance for how the hull resistance may be better managed. Many studies have found that a significant portion of coastal invasive aquatic species (IAS) have been introduced via ship hull fouling in addition to those introduced via vessels' ballast water discharges. Consequently the International Maritime Organization (IMO) has developed voluntary guidelines, IMO MEPC.207(62), to minimize the risk of further spread of IAS. In line with the IMO guidelines, some US states have also started the process of making similar guidelines mandatory through laws. The State of California is one such example.