Cryptorchidism is a congenital condition in which one or both testicles are not appropriately positioned in the scrotum at birth and cannot be moved into the proper position manually. The term "cryptorchidism" literally means "hidden testicle" and is often used interchangeably with the term "undescended testicle." It affects an estimated 3 percent of full-term male neonates and up to 30 percent of premature male infants, making it the most common male genital anomaly identified at birth. The etiology of cryptorchidism is not well understood, and the undescended testicles may be palpable or nonpalpable. Clinical decisionmaking about treatment is influenced by many factors, including whether or not the testicle is palpable, whether the condition is present unilaterally or bilaterally, the age at presentation, and coexisting medical conditions. Once cryptorchidism is diagnosed, treatment choices may include watchful waiting, hormonal treatment, or surgery. Decisions about which clinical pathway to follow may be guided by results of hormonal stimulation testing and/or imaging, particularly when the testicle is nonpalpable. Clinical uncertainty and lack of guidance exist on the appropriate clinical pathway for treatment of cryptorchidism. Areas of uncertainty include selecting the optimal approach to treatment planning (imaging vs. no imaging, hormonal stimulation testing or not) and intervention (surgical vs. hormonal, one-stage vs. two-stage FS, various modifications of each of the surgical techniques, and open vs. laparoscopic approach). The immediate goal of most interventions for cryptorchidism is to reposition the undescended gonad in a "normal" position in the scrotum. Intermediate outcomes include psychological benefits in terms of body image, and long-term goals include preservation of fertility and prevention of testicular malignancy. All of these outcomes are important to patients.This review focuses on the effectiveness of imaging for identifying and correctly locating testicles, on the use of hormonal stimulation for identifying anorchia in treatment planning, on hormones for achieving testicular descent, and on choices among surgical treatments, including surgical approach (open vs. laparoscopic). We have synthesized evidence in the published literature to address the following Key Questions (KQs) and population, interventions, comparators, outcomes, timing, and settings (PICOTS). KQ1a. For determining a course of treatment, is imaging equivalent to laparoscopy in determining the presence and location of a nonpalpable testicle? KQ1b. In male children with bilateral nonpalpable testicles, does the use of hormonal stimulation testing reduce the need for surgery as part of a treatment plan? KQ2. What is the effectiveness of initial hormonal therapy (human chorionic gonadotropin or luteinizing hormone-releasing hormone) for the treatment of cryptorchidism for outcomes, including but not limited to: Further surgical intervention, The effect on infertility/subfertility, The development of testicular malignancy, The size, location, and function of the testicles. KQ3. What is the effectiveness of surgical therapies (one-stage vs. two-stage, laparoscopic vs. open approach) for the treatment of cryptorchidism for outcomes, including but not limited to: Further surgical intervention, The effect on infertility/subfertility, The development of testicular malignancy, The size, location, and function of the testicles. KQ4. How do the age at presentation, physical presentation of cryptorchidism (unilateral vs. bilateral, palpable vs. nonpalpable, anatomic location), and occurrence of associated abnormalities (e.g., hernia) modify diagnosis, treatment, and outcomes? KQ5. What are the nature and frequency of harms associated with workup or treatment for cryptorchidism?