Survey on the occurrence of diseases, respectively, on 641 and 144 germplasm lines of lentil and countrybean and study on the effect of date of sowing on the incidence of major diseases in the selected lines of the two crops, and their reaction to the selected major diseases were observed under natural field conditions in the performance trial plots of the Genetics and Plant Breeding Department at BAU Farm, Mymensingh during rabi season of 1989-90. Reaction of promising lines of lentil to foot rot pathogen Sclerotium rolfsii, was also determined through artificial inoculation in the net house of the Department of Plant Pathology. Altogether 11 diseases of lentil and 6 diseases of countrybean were recorded. Of all the diseases, anthracnose of lentil caused by Colletotrichum dematium and bacterial leaf spot of countrybean caused by Xanthomonas sp. appear to be new records for the country. Sowing of lentil during 3rd week of November was found to reduce the incidence of foot & root rot compared to early sowing; while sowing time had no influence on the incidence of bean common mosaic in case of countrybean. Reaction of selected lines of lentil to foot & root rot (Sclerotium rolfsii and Fusarium oxysporum) and bushy stunt (Mycoplasma) pathogens showed that four lines—502, 513, 681 and 1185 were resistant under natural field conditions. Similarly, two lines—DS-30 and DS-52 of countrybean were found to be resistant against anthracnose (Colletotrichum lindemuthianum) and Cercospora leaf spot (Cercospora cruenta) pathogens under natural field conditions. Artificial inoculation test of 10 selected genotypes of lentil to foot rot pathogen, Sclerotium rolfsii showed that all the lines were susceptible to the test pathogen.