There are various approaches and options for radical nephrectomy (RN) for renal cell carcinoma (RCC): an open or laparoscopic approach; transperitoneally or retroperitoneally; via a single port, multiple ports, or a small incision; and with the patient in the supine position or flank position. However, the current RCC guidelines recommend the laparoscopic approach as the standard treatment or preferred option for T2 RCC patients [
1,
2]. Laparoendoscopic single-port surgery (LESS)-RN was recently developed. In LESS-RN, all instruments are inserted via a small incision with [
3] or without carbon dioxide [
4‐
6]. For LESS-RN without carbon dioxide, Kihara et al. [
7] developed gasless laparoendoscopic single-port surgery RN (GasLESSRN), which was previously termed “portless endoscopic urologic surgery” (PLES) [
5] or “minimum incision endoscopic surgery” (MIES) [
6]. GasLESSRN is performed retroperitoneally in the flank position via a small incision 4–6 cm long under endoscopic magnification; it is performed in combination with stereovision and without carbon dioxide, trocar ports, or inserting the hands into the operative field. This procedure has been demonstrated to be a safe, feasible, cost-effective, and minimally invasive treatment option for T1–3 RCC with oncologic outcomes equivalent to those with conventional open radical nephrectomy [
8]. However, GasLESSRN has several advantages: (1) the small incision as a single port, which permits the extraction of the kidney covered with Gerota’s fascia, is aesthetically advantageous; (2) carbon dioxide, which is a greenhouse gas associated with climate change [
9] and confers a risk of pneumoperitoneum [
10‐
12], is not required [
13]; (3) the surgery uses reusable instruments, reducing waste and costs [
14,
15], which is particularly advantageous in developing countries. The cost-effectiveness, smaller environmental impact, and minimal invasiveness of GasLESSRN collectively warrant the pursuit of this technique. On the other hand, the positioning and type of incision are important initial steps for successful surgery without complications; they should be chosen according to the disease status, patient’s condition, and surgeon’s experience. We occasionally encounter RCC patients suitable for supine positioning rather than flank positioning for RN; these patients have conditions such as renal venous and/or arterial anomalies, lung diseases, and skeletal diseases or deformities as shown in living donor kidney harvesting [
16]. Therefore, we adopted an approach via a small retroperitoneal anterior subcostal incision (RASI) in the supine position for RN, especially for GasLESSRN. Here, we present our initial experience and the details of an approach via a small RASI in the supine position for GasLESSRN, which is termed “RASI-GasLESSRN” herein.