This study was carried out to investigate the heavy metal and microbiological hazards on by-products (liver, omasum, small intestines) of cattle. From April to October in 2011, one hundred and twenty samples were equally collected from slaughterhouse and meat by-product markets in Incheon city. The total bacteria counts and E. coli count were applied to assess the microbiological quality. Food borne bacteria including Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, Clostridium perfringens and E. coli O157:H7 were also determined. The results were obtained as follows: The undesirable grade (more than $10^5;CFU/cm^2$) was detected in the by-product from 18.3% (slaughterhouse) and 23.3% (by-product markets). The frequency of generic E. coli (more than $10^2;CFU/cm^2$) from the slaughterhouse was 20.0%, whereas that of the meat by-product markets was 26.7%. Of the samples from slaughterhouse, 3 (5.0%), 5 (8.3%), and 12 (20.0%) samples were contaminated with Salmonella spp, S. aureus, and C. perfringens, respectively. S. aureus and C. perfringens were also detected in 6 (10.0%) and 25 (41.7%) samples in the meat by-product markets, respectively. Nine of 11 S. aureus isolates harbored toxin gene. However, the cpe gene of C. perfringens was not detected among the 37 isolates. The detection rate was higher in August than in February, April and June. The levels of Cd and Pb in all the samples tended to be low (<0.2 mg/kg). This preliminary data could be used for legislation on the regulation and control of microorganism and heavy metal in by-products of cattle.