Small-angle neutron scattering (SANS) is used with the "high-concentration" method to extract single-particle scattering from single-wall carbon nanotubes (SWNTs). The SWNT material was labeled by covalently attaching -C4H9 or -C4D9 groups by use of free radical chemistry. Mixtures of SWNT-C4H9 and SWNT-C4D9 were dispersed in D2O containing 1% sodium lauryl sulfate-d(23) (SLS) by use of sonication. SLS matches the neutron contrast of D2O so that all of the SANS is due to the labeled SWNT. Thermogravinietric analysis shows that mass fractions of butyl groups attached to the SWNT-C4H9 and the SWNT-C4D9 were well matched. The scattering had a power law of -2.5, which is characteristic of a "particle" made of clustered SWNTs. The clustering seen in SWNT scattering is due to collections of SWNTs that do not exchange in a dynamic equilibrium with other nanotubes.