Abstract: Sucker rod connections are provided, preferably for rods with ?? to 1?? diameter, with improved fatigue resistance, formed by applying diametrical interference to prevent disengagement, reducing axial interference between the pin shoulder of a male member and the box shoulder of a female member. The connection may comprise a tapered threaded connection and trapezoidal threads, where contact among threads is flank-to-flank, load and stab, the crest of the thread being a little larger than the root of the thread. Each rod may have from about 4 to 10 threads per inch, preferably about 6 and 10 threads per inch (25.4 mm), the thread flank angle ranges from about 2° to 10°, preferably about 3° with a line perpendicular to the connection axis, and the connection taper is from about 1/15 to 1/30 relative to diameters of the connection. The flank-to-flank contact improves fatigue performance and the width and angle of the threads are determined considering a very low plastic thread deformation.