Acute lymphoblastic leukemia is a fascinating disease for the cytogeneticist, as so many cases have a clone detectable by cytogenetics or FISH, and because identifying the abnormalities provides such useful information to the clinician. However, it is also a frustrating disease, as it has technical challenges such as a marked tendency for the sample to clot during harvesting, frequently poor chromosome morphology, and, especially in the high count cases, failure to provide any divisions at all for analysis. For these reasons, this book includes two chapters on the practical aspects of undertaking cytogenetic studies in ALL to illustrate contrasting approaches. The first is from a laboratory that is a world leader in its success rates, which has an enviably low sample/cytogeneticist ratio, and which is usually able to expect a good-sized sample commensurate with the importance given to a diagnostic cytogenetic study. The second is from a laboratory that also has a good success rate, despite having to cope with a higher workload and often much smaller samples. This is not to imply that each technique is limited to such circumstances; both are worthy of study and emulation.