The treatment of lymphomas may result in the development of second malignancies, as evident by the numerous reports in the literature. Treatment with cyclophosphamide-based chemotherapy regimens may lead to bladder lesions such as haemorrhagic cystitis and also to carcinoma of the urinary bladder. Previous pelvic radiotherapy treatment is also implicated as a cause for local second cancers. We present the case of a patient treated for Hodgkin's lymphoma, who was diagnosed with transitional cell carcinoma of the bladder soon after treatment completion. On completion of 6 cycles of ABVD chemotherapy the patient was on follow-up. Two months after treatment completion the patient complained of dysuria and was investigated for a suspected urinary tract infection. Urine microscopy did not reveal any abnormality. Symptomatic treatment was prescribed and cystoscopy was arranged. The cystoscopic findings suggested an irregular growth overlying the trigone and the biopsy reported it as transitional cell carcinoma. This case report demonstrates that symptoms attributed to common medical causes in patients treated for cancer may be a sign of second malignancy. This case report also demonstrates the need for a thorough evaluation of patients' complaints during follow-up, although the likelihood for the occurrence of a second malignancy may be low. The assumption that these symptoms were due to a commonly occurring urinary tract infection would have had serious implications leading to a delay in the treatment of the bladder cancer.