Exposure to ionizing radiation has been well known to cause serious effects to human health such as cancer and cardiovascular diseases. Various biological dosimetry(biodosimetry) assays are available to estimate absorbed radiation dose. The only technique available currently to analyze stable chromosome aberrations is Fluorescence in Situ Hybridization (FISH) assay. This study demonstrated the method development of FISH whole chromosome painting to detect translocation in chromosome 1,2 and 4.A volume of 1 ml heparinized blood was cultured promptly with 10 ml of complete medium and 300 µl phytohaemagglutinin. Sample was incubated at 37°C for 48 hours, and colcemid was added at the 45th hour. Next, 5 ml of 0.075 M KCL (at 37°C) was added to the cultured sample and fixed with 5 ml methanol/acetic acid (3:1) solution prior to five cycles centrifugation. An amount of 10 µl cell pellet was dropped at about 5cm distance perpendicular onto a cold slide. Later, 7 µl XCP Mix #1-#2-#4, 3 color probe was applied before hybridization in a humidified chamber at 37°C for at least 1 hour or overnight. Post hybridization washes was done with 0.4X SSC at 72°C for 2 minutes, later with 2X SSC and 0.05% Tween 20 with pH 7 at room temperature for 30 seconds. Finally,7 µl of DAPI counterstain was applied. Images were captured using Zeiss microscope, Metafer 4 and ISIS software. Each chromosome 1,2 and 4 were labelled respectively orange, green and a combination of both colours. Most images captured were distinct with an average 500-800 metaphases each slide. The same image quality was shown from both 1-hour and overnight hybridization. Images obtained were satisfactory to assess radiation exposure by estimating the biological absorb dose in further study that require translocation analysis of 500 until 1000 metaphases per individual.