The experiment was conducted at the experimental farm of Bangladesh Institute of Nuclear Agriculture, Mymensingh, during July 2011 to December 2012. Geographically the experimental area is located at 24075 N latitude and 9005 E longitudes at the elevation of 18 m above the sea level. The field was medium high land. The soil of the experimental site belonging under the agro-ecological zone of Old Brahmaputra Floodplain (AEZ-9). The experimental field area was under sub-tropical climates characterized by heavy rainfall during the month of April to September and scanty rainfall during October to March. Fifty four rice landraces (i.e. Dudh kalam, Hati bajore, Malagoti, Kuchra, Enghi, Kajol shail, Hogla, Jamai naru, Hari, Dakh shail, Moina moti, Marish shail, Patnai, Bhute shallot, Kute patnai, Mohini shallot, Moghai balam, Sada gotal, Khak shail, Mohime, Holde gotal, Jota balam, Tilek kuchi, Rani Shalot, Kathi goccha, Bashful balam, Bazra muri, Durga bhog, Kumra ghor, Khainol, Ghunshi, Chinikani, Dhar shail, Khejur chori, Shaheb kachi, Raja shail, Hamai, Mura bajal, Lal gotal, Kalmilata, Volanath, Rupessor, Sylhet balam, Karengal, Kalo mota, Mota aman, Ghochi, Chap shail, Mondeshor, Nona kochi, Ghocca, Tal mugur, Ghigoj and Tor balam) were collected from the farmer’s field of southern Bangladesh. Rest of the rice genotypes (21 landraces i.e. Fulkainja, Piarjat, Koicha binni, Lal biroi, Lalanamia, Golapi, Asam binni, Kakua binni, Nona bokhra, Jongli boro, Kashrail, Ledra binni, Nunnia, Rotisail, Genggeng binni, Chinisail, Jolkumri, Ponkhiraj, Mowbinni, Bogi, Kali boro and Binadhan-8) was collected from Plant Breeding Division, BINA, Mymensingh. The experiment was laid out in a Randomized Complete Block Design (RCBD) with three replications. The experimental field was divided into three blocks each representing one replication. Each block was then sub-divided in to seventy-six plots. The seventy-six rice genotypes were placed in each plot. The size of the unit plot was one square meter in size. Row to row and plant to plant distances were 20 cm and 20 cm, respectively in each plot. Data were recorded on off-types from per plot in each block, which were not identified at earlier during seed processing after collection. Among the studied characters, number of off-types meter -2 and types of off-types meter -2 were recorded in the field and the remaining two characters were calculated and recorded in the laboratory, which were as follows: By regular field visits, off-types were identified in each plots and marking of off-types with tag was done on a regular basis. Panicles of the off-types were covered with bags made of glossy papers to avoid further out crossing in order to maintain genetic purity of the rice genotypes of the plot. Selection criteria for off-types at different stages of crops followed in this experiment is shown. The land was free from volunteer plants. At harvesting stage, off-types were classified into different types based on the plant height,difference in seed size, shape, presence or absence of awns and seed coat color. Similarities of these characters among the off-types were considered as same off-type genotypes in this experiment. One thousand clean sun dried grains were counted from the sample plant by seed counter after which weighed (g) was taken at 14% seed moisture content (with husk). After first round of the purification, a second round of purification was done and seeds are preserved at the germplasm of Plant Breeding Division, BINA, Mymensingh. Analysis of variance was performed using the plant breeding statistical program.