The Cucumis melo-Pseudoperonospora cubensis host-pathogen interaction is characterized by large variation in specificity. This report summarizes results obtained by laboratory screening of 52 C. melo accessions by 8 isolates of P cubensis. The isolates represent 8 different pathotypes with low, medium or high levels of pathogenicity. The reaction of C. melo accessions was evaluated on leaf discs removed from adult plants; sporulation intensity of P cubensis isolates was measured 6 to 14 days after inoculation. Relatively little variability in reaction patterns to P cubensis isolates was detected. The majority of C. melo accessions was highly susceptible to most of the P cubensis isolates studied. Altogether, 39 C. me lo accessions showed susceptibility to all 8 isolates. Relatively few accessions expressed incomplete resistance (8 accessions in 15 interactions with P cubensis isolates) or heterogenous reactions (8 accessions in 13 interactions). Only one accession (PI 315410) was found to be highly resistant to some P cubensis isolates. Among studied C. melo accessions, 14 different reaction patterns can be distinguished based on qualitative differences in response to this set of P cubensis isolates.