The DEGREE-Δ CLOSEST PHYLOGENETIC kTH ROOT PROBLEM (ΔCPR k ) is the problem of finding a (phylogenetic) tree T from a given graph G = (V , E) such that (1) the degree of each internal node in T is at least 3 and at most Δ, (2) the external nodes (i.e. leaves) of T are exactly the elements of V , and (3) the number of disagreements, i.e., |E ⊕ {{u, v} : u, v are leaves of T and (u, v) denotes the distance between u and v in tree T . This problem arises from theoretical studies in evolutionary biology and generalizes several important combinatorial optimization problems such as the maximum matching problem. Unfortunately, it is known to be NP-hard for all fixed constants Δ, k such that either both Δ ≥ 3 and k ≥ 3, or Δ > 3 and k = 2. This paper presents a polynomial-time 8-approximation algorithm for ΔCPR 2 for any fixed Δ > 3, a quadratic-time 12-approximation algorithm for 3CPR 3 , and a polynomialtime approximation scheme for the maximization version of ΔCPR k for any fixed Δ and k.