Karyotypic analysis provides useful diagnostic information in many haematological malignancies. However, standard metaphase cytogenetics has technical limitations that result in the underestimation of the degree of chromosomal changes. Array-based technologies can be used for karyotyping and can supplant some of the shortcomings of metaphase cytogenetics, and include single nucleotide polymorphism arrays (SNP-A) and comparative genomic hybridization arrays (CGH-A). Array-based cytogenetic tools do not rely on cell division, have superb resolution for unbalanced lesions and allow for the detection of copy number-neutral loss of heterozygosity, a type of lesion not seen with metaphase cytogenetics. Moreover, genomic array analysis is automated and results can be objectively and systematically analysed using biostatistical algorithms. As a potential advantage over genomic approaches, metaphase cytogenetics can detect balanced chromosomal defects and resolves clonal mosaicism. Initial studies performed in various haematological malignancies indicate the potential of SNP-A-based karyotyping as a useful clinical cytogenetic detection tool. The current effort is aimed at developing rational diagnostic algorithms for the detection of somatic defects and the establishment of clinical correlations for novel SNP-A-detected chromosomal defects, including acquired somatic uniparental disomy. SNP-A can complement metaphase karyotyping and will probably play an important role in clinical cytogenetic diagnostics.