Single crystals were grown from affinity-purified stinging nettle lectin and from its complex with the specific trisaccharide NN'N"-triacetylchitotriose by vapor diffusion at room temperature. The lectin crystallizes in space group P2(1)2(1)2(1) with unit cell dimensions a = 54.3 (1) A, b = 62.2 (1) A, and c = 92.4 (2) A, and diffracts to 3.0 A resolution. The asymmetric unit contains three lectin monomers. The crystals of the lectin-trisaccharide complex have space group P2(1)2(1)2(1) with cell constants a = 37.69 (4) A, b = 48.97 (6) A, and c = 57.32 (4) A. These crystals diffract to at least 2.0 A resolution and the asymmetric unit contains one lectin monomer. A three-dimensional X-ray structure determination is on its way.