We present the case of a 3.5-year-old Iranian girl who was referred to us from pediatric surgery clinic because of a gluteal mass. Her parents informed us that the swelling of the right buttock of their daughter had been present since her birth. The size of the mass had been increasing gradually. They did not mention any bowel or bladder dysfunctions. A local physician had aspirated the cyst twice, 8 and 4 months prior to this presentation. Clear fluid had been aspirated each time, bur the mass would always reappear after several weeks. Unfortunately the results of the chemical analysis of the fluid were not available. A physical examination of our patient showed a soft, 3 × 4-cm fluctuant and non-pulsatile mass over her gluteal region. It was completely covered with normal skin without any vascular or hairy stigmata. The size of this mass did not increase with crying or coughing. Her transillumination test results were positive. Her midline was normal, with no sinus tract or swelling. Results of her sensory, rectal tone and lower limbs motor exams were within normal limits. No abnormal skin lesions or skeletal deformities were found. The curvature of her spinal column appeared normal. Results of her routine laboratory investigations were also normal. An anteroposterior X-ray examination of her lumbosacral region showed spina bifida of the L5 and S1 vertebrae. An ultrasound scan showed a very well-defined purely cystic, oblong lesion measuring 3.7 × 4.5 × 2.2 cm in size in our patient's right upper gluteal region under the gluteal muscles. There was no evidence of internal echoes or solid component or septae within the sac. We planned to perform myelography but unfortunately found it impossible because of our patient's allergic sensitivity to the contrast agent (omnipaque). A lumosacral magnetic resonance imaging (MRI) showed a well-defined cystic mass measuring 36 × 21 × 45 mm in her right buttock. The cystic mass appeared as a low signal intensity area on T1-weighted images and a high signal intensity area on T2-weighted images, which was similar to her cerebrospinal fluid (CSF) signal. No obvious communication between the cyst and the spinal canal was perceivable. The position and shape of the cord, roots and lying of the conus were unremarkable. The findings were suggestive of lateral meningocele. A voiding cystourethrography showed a normal voiding pattern of our patient's bladder and urethra. There was no evidence of vesicoureteral reflux. We then decided to perform resective surgery. After performing a transverse incision at the equator of our patient's lesion, we found a cystic, relatively thin-walled mass with a smooth pink exterior layer and a shiny creamy interior surface lying under the right gluteal muscles. We aspirated the cyst and clear fluid came out of it. Opening the cyst, we saw a very small aperture at the level of the ilium. We further extended the hole using microdrill and Kerrison punch along the tract, through which we saw communication between the cyst and the thecal sac through the spina bifida at the sacral canal. No neural tissue was found lying inside. After performing a ligature of the aperture of the cyst, we resected the walls and we closed the wound in layers. Our patient's postoperative recovery was uneventful. On histopathology, we found that the wall of the sac was composed of fibrous tissue that had a lining of flattened to cuboidal epithelium. Polymorphonuclear leukocytes, histiocytes, and giant cells were also noted. The final pathological diagnosis was reported to be a meningocele with inflammatory reaction. Analysis of her intracystic fluid showed the following: red blood cells = 100/cc, white blood cells = 2500/cc (polymorphonuclear = 72%, lymphocyte = 28%), glucose = 60 mg/dl and protein = 45 mg/dl. Our patient was found asymptomatic when she was presented for follow-up examination after 18 months.