The well-known phosphoramidite chemistry routinely used in solid-phase oligonucleotide synthesis is exploited here in the preparation of steroid conjugates in solution. The applicability of the method is tested by conjugating one nucleosidic and one non-nucleosidic phosphoramidite building block to 11-alpha-hydroxyprogesterone. The suitability of one of the conjugates synthesized (5) for a competitive binding assay is also demonstrated.