Experiments on the abundance of groundnut aphid, Aphis craccivora Koch. on different groundnut cultivars were carried out in the Genetics and Plant Breeding Field Laboratory, Bangladesh Agricultural University, Mymensingh, during the period from November, 2000 to May, 2001. Thirty groundnut cultivars viz. ICGV 92109, ICGV 92113, ICGV 92116, ICGV 92118, ICGV 92120, ICGV 92121, ICGV 92126, ICGV 93232, ICGV 93233, ICGV 93225, ICGV 93260, ICGV 93261, ICGV 93269, ICGV 93277, ICGV 86635, Dhaka- 1, Cv. 9276, Cv. 4595, Cv. 3203, ICGV 88388, ICGV 86707, M-5, Cv. 65/1484, ACC- 12, ICGS-E-55, DG-2, ICGE-55, ICGV 89259, ICGS-76 and DM-1 were planted on 26 November, 2000 and observations on aphid populations and infested groundnut plants were recorded weekly starting from 45 days after planting. A total of eight samples were taken throughout the crop period. The results indicated that the abundance of aphids gradually increased from 45 days after planting and reached the peak at 73 days, and then aphid population gradually declined. Among the cultivars tested, the cultivar DG-2 was found highly susceptible to aphid and ICGV 86635 was less susceptible. The reasons for high aphid population at 73 days after planting and reactions of different cultivars to aphid attack were discussed.