Comparative genomic hybridization (CGH) was used to analyse 34 follicular lymphoma (FL) samples. 27 samples showed DNA sequence copy number changes of at least one genomic region (26 samples with at least one gain and nine with at least one loss). Some chromosomes or chromosomal regions were preferentially involved. The most frequently gained regions were chromosome 18q (29% of samples), chromosome X (21%), chromosome 7 (18%), chromosomes 2, 6p and 8q (12%). Two regions were preferentially lost: 6q (12%) and 17p (9%). All these gained and lost regions have been previously reported in cytogenetic studies, confirming the accuracy of CGH in detecting genetic abnormalities in FL. 21% of samples displayed normal profiles, probably reflecting the absence of unbalanced abnormality, which is also in agreement with the cytogenetic data. In conclusion, we showed that CGH is an accurate, reliable and rapid method and we propose the inclusion of CGH in the evaluation of FL at diagnosis.