I study the adsorption of paramagnetic colloids to one-dimensional nanomagnets. It is found that in the absence of external magnetic fields the colloids tend to adsorb to the nanomagnet by arranging themselves in a nearly close-packed formation, whereas in an external field some of the colloids are repelled due to dipolar interactions. I develop a theory for this phenomenon and show that it is in agreement with experimental data. (c) 2006 Elsevier Inc. All rights reserved.