Sweet potato genotypes obtained from the Philippine Root Crop Research and Training Center [Baybay, Leyte, Philippines] and the Dept. of Agricultural Botany and Plant Breeding germplasm collection were screened for resistance to major postharvest diseases found in the Philippines. Likewise, the nature of disease development as affected by host resistance was evaluated. Assessment of 328 varieties/accessions of sweet potato to major postharvest diseases showed that 15% were resistant to Botryodiplodia theobromae, 5% to Macrophomina phaseolina and 3% to both M. phaseolina and B. theobromae. Seventy seven percent were rated moderately resistant to susceptible. In resistant varieties, the pathogens was noted to penetrate only a few millimeters of the host tissues, then followed by inhibition of growth of the pathogens. Whereas, in susceptible sweet potato roots, the pathogen spreads fast and infected the whole roots for about 4 to 6 days after inoculation.