This paper describes a parametric study of drill string threaded connector design based on a ＇＇factorial design＇＇ method. The study is facilitated by a hybrid model which has been developed, validated, and reported previously enabling efficient calculation of load and stress distribution along threaded connectors subjected to both axial and bending modes of loading. A parametric equation is produced where stress concentration factor is defined in terms of various geometrical variables. The equation is then utilized to carry out a constrained optimization within the feasible parameter space, and hence produce an ＇＇optimum＇＇ thread and connector design.