Prostatic infarcts are uncommon and in the past have only been reported on transurethral resections of the prostate. We reviewed 13 consults and 2 nonconsult cases of needle biopsies showing prostatic infarcts from two institutions. The incidence of infarcts on biopsy were 2 in 2958 (0.07%) and 1 in 108,586 (0.0009%) in our nonconsult cases. Men averaged 71 years of age (range, 57-84 yrs). No relationship was seen with histories of hypertension, diabetes, atherosclerotic coronary vascular disease, recent surgery, and steroid use. Four of 12 men with available information had acute urinary retention, with markedly enlarged prostates in three (90 cc, 92 cc, 94 cc); two of these men had hematuria. An additional two men also had large glands (84 cc, 150 cc), one also with hematuria. Of eight men without acute urinary retention, three had sudden prostate-specific antigen (PSA) rises (increases of 199 ng/mL, 219 ng/mL, 287 ng/mL). Infarcts were usually an isolated focus on one core and varied from 1 mm to 11 mm (mean, 6.3 mm). Six cases showed earlier-aged infarcts with coagulative necrosis and recent hemorrhage and six showed intermediate-aged infarcts with reactive stroma and epithelium without necrosis. In the remaining three cases, there were remote infarcts characterized by replacement of the stroma by dense fibrosis with metaplastic glands. Adjacent tissue revealed reactive nests of immature squamous metaplasia in 14 of 15 cases with visible nucleoli (12 cases), squamous atypia (7 cases), and mitoses ranging from 1-10 (7 cases). Pathologists sent in 10 of 13 consult cases (77%) for problems with interpretation of the infarcts; remaining consults had other pathology of concern. One case was misdiagnosed as urothelial cancer. Features helpful in recognizing infarcts' benign nature were cyst formation containing cellular debris with or without neutrophils (73%), corpora amylacea (20%), and rings of collagen around squamous islands (40%). Infarcts are typically, although not exclusively, found in large prostates and may result in sudden rises in serum PSA. Infarcts' distinctive histology must be recognized and distinguished from necrosis resulting from infection and prior cryotherapy, as we have seen such misdiagnoses. Pathologists' awareness of prostatic infarcts on needle biopsy and their potential for atypical histology can prevent the misdiagnosis of cancer.