A theorem is proved that every resolvable BIB-design (v,k,λ) with λ=k−1 and the parameters v and k such that there exists a set of k−1 pairwise orthogonal Latin squares of order v can be embedded in a resolvable BIB-design ((k+1)v, k, k−1). An analogous theorem is established for the class of arbitrary BIB-designs. As a consequence is deduced the existence of resolvable BIB-designs (v,k,λ) with λ=k−1 and λ=(k−1)/2.