Despite tremendous improvements in the outcome of patients with multiple myeloma (MM) in the past decade, high-risk patients have not benefited from the approval of novel drugs. The most important prognostic factor is the loss of parts of the short arm of chromosome 17, known as deletion 17p (del(17p)). A recent publication (on a small number of patients) suggested that these patients are at very high-risk only if del(17p) is associated with TP53 mutations, the so-called "double-hit" population. To validate this finding, we designed a much larger study on 121 patients presenting del(17p) in >55% of their plasma cells, and homogeneously treated by an intensive approach. For these 121 patients, we performed deep next generation sequencing targeted on TP53. The outcome was then compared to a large control population (2505 patients lacking del(17p)). Our results confirmed that the "double hit" situation is the worst (median survival = 36 months), but that del(17p) alone also confers a poor outcome compared with the control cohort (median survival = 52.8 months vs 152.2 months, respectively). In conclusion, our study clearly confirms the extremely poor outcome of patients displaying "double hit", but also that del(17p) alone is still a very high-risk feature, confirming its value as a prognostic indicator for poor outcome.