Single-walled carbon nanotubes ( SWNTs) are exfoliated and functionalized into small bundles and individuals by vigorous stirring "on water" in the presence of a substituted aniline and an oxidizing agent. This is an example of an "on water" reaction that leads to functionalized SWNTs, and it represents a "green", or environmentally friendly, process. A variety of reaction conditions were explored. The products were analyzed with Raman, UV-vis-NIR, and X-ray photoelectron spectroscopies, atomic force and transmission electron microscopies, and thermogravimetric analysis.