This paper reviews the role of low-grade dysplasia (LGD) as a marker of progression in Barrett's oesophagus (BO). Albeit with its limits due to the difficulty of its diagnosis and the low agreement among pathologists, LGD remains the most relevant single prognostic factor of progression, and, when the diagnosis is confirmed by two or three pathologists, the chances of progression to high-grade dysplasia or invasive adenocarcinoma are as high as 40%. On the other hand, BO patients who remain dysplasia free at several follow-up examinations seem to have a very low likelihood of progression. The diagnosis of LGD should be confirmed by two pathologists, and surveillance programs should be tailored depending on the presence or persistent absence of LGD. Ablative therapy should be also considered for cases where LGD persists in a series of follow-ups.