The purpose of this research was to correlate non-random chromosomal aberrations in the peripheral blood lymphocytes (PBLs) of prostate cancer patients with specific clinical parameters. Peripheral blood samples were analyzed from 59 informative prostate cancer patients. Non-random chromosomal alterations detected in the PBLs and their correlation with any specific clinical parameters were analyzed statistically. A comparison was made between specific chromosomal abnormalities in the patients having an early (<65 years) or late (greater than or equal to 65 years) age at disease onset, low-grade (Gleason grade <7) or high-grade (Gleason grade greater than or equal to 7) turners, a low (<10 ng/ml) or high (greater than or equal to 10 ng/ml) prostate-specific antigen (PSA) level, and androgen-sensitive or -insensitive disease. In examining the specific chromosomal breakpoints, the regions 1p13, 2q21, 3p21, 4q13, 5q31, 6p21, 7p15, 7p13, 7q32, 10p11, 10q26, 11p15, 11p11, 14q12, and 16q12 showed breaks in at least four cases. Chromosome 15 (P=0.045) was significantly altered in patients having a PSA value greater than or equal to 10, while it (P=0.017) and chromosome 19 (P=0.036) were significantly altered in patients having a PSA value greater than or equal to 20. In addition, chromosomes 5 (P=0.032), 8 (P=0.020), 16 (P=0.009), and 20 (P=0.047) were significantly altered in patients having a Gleason grade greater than 7. Also, chromosomes 2 (P=0.020) and 3 (P=0.044) were significantly altered in patients who had early disease onset. Additionally, chromosome 10 (P=0.041) was significantly altered in patients having metastasis, and chromosomes 4 (P=0.006) and 7 (P=0.028) were significantly altered in patients having androgen-insensitive disease. In spite of the small subset of patients, chromosome 8 (P=0.003) was significantly altered in patients having small cell carcinoma of the prostate. From these results we conclude that nonrandom chromosomal aberrations present in PBLs of prostate cancer patients can be correlated with specific clinical parameters. These correlations can be used to identify a prostate cancer patient's risk response to therapy.