OBJECTIVE To report the clinical spectrum seen in young abusers of street‐ketamine (regular recreational abusers of street‐ketamine, for its hallucinogenic effects) in Hong Kong, presenting with significant lower urinary tract symptoms (LUTS) but with no evidence of bacterial infection. PATIENTS AND METHODS We retrospectively analysed the clinical presentations, pelvic pain and urgency/frequency scores, video‐urodynamic studies, cystoscopy findings, histological features of bladder biopsies and radiological findings of 59 ketamine abusers who were referred to the urology units of Princess Margaret and Tuen Mun Hospital, Hong Kong, from March 2000 to December 2007. RESULTS Of the 59 patients, all had moderate to severe LUTS, i.e. frequency, urgency, dysuria, urge incontinence and occasionally painful haematuria. Forty‐two (71%) patients had a cystoscopy that showed various degrees of epithelial inflammation similar to that seen in chronic interstitial cystitis. All of 12 available bladder biopsies had histological features resembling those of interstitial cystitis. Urodynamically, either detrusor overactivity or decreased bladder compliance with or without vesico‐ureteric reflux was detected to some degree in all of 47 patients. Thirty patients (51%) had unilateral or bilateral hydronephrosis on renal ultrasonography, and four (7%) showed features suggestive of papillary necrosis on radiological imaging. Eight patients had a raised serum creatinine level. CONCLUSION A syndrome of cystitis and contracted bladder can be associated with street‐ketamine abuse. Secondary renal damage can occur in severe cases which might be irreversible, rendering patients dependent on dialysis. The present data do not establish the precise cause nor the incidence. Street‐ketamine abuse is not only a drug problem, but might be associated with a serious urological condition causing a significant burden to healthcare resources.