A biotin derivative, namely biotin-aminocaproic acid-lysine (BAL), was synthesized with solid-phase chemistry, conjugated to a carrier-protein, and used for rabbit immunization. The aminocaproic acid-lysine "long-arm" was used in order to project the biotin-hapten above the carrier-protein surface. Lysine was selected due to its N(epsilon)-amino group, through which BAL was conjugated to the carrier-protein. BAL was synthesized on a commercially available resin with the Fmoc-solid-phase strategy; this has simplified the experimental procedure, overcome the need for intermediate purification steps, and led to a final product of high purity, with high yield. The anti-BAL antibodies recognized free biotin, as shown with an in-house-developed ELISA, in which biotin conjugated to a synthetic "lysine-dendrimer" was used to coat the ELISA microwells. In immunocytology and Western-blot experiments, the anti-BAL antibodies led to similar results with those obtained with streptavidin. Synthetic derivatives of hapten molecules that can be easily prepared with solid-phase chemistry, such as BAL, may be used for the development of specific antibodies for the corresponding hapten.