Thalidomide attenuates NO mediated blood capillaries in invitro egg yolk angiogenesis. Fourth day incubated chicken eggs were broken, entire egg contents were transferred in sterilized petri dish and their vascular beds were treated with 500 μM SNP and incubated at 37°C/5% CO2 for 6 hours. Next, different (25, 50, and 75 μg/ml) concentrations of thalidomide was added to SNP treated vascular beds respectively and incubated for another 6 hours. Images were taken at 0 hours, 6 hours and 12 hours that show that SNP promoted blood vessel formation in the vascular bed in 6 hours (indicated by arrows). All the three concentrations of thalidomide were found to retard SNP mediated growth of blood capillaries at the end of 12 hours incubation.