Seven hundred ninety six milk samples from 266 quarters of 69 lactating cows were subjected to microbiological investigations for identification of pathogens. One hundred ninety bacterial isolates were recovered from 89 infected quarters, among these monomicrobial infection was found in 50 (56.2%) quarters, whereas, mixed infection was observed in 39 (43.8%) quarters. Bacterial isolates identified were Staph. chromogenes (49.47%), Staph. hyicus (21.1%), Staph. epidermidis (11.05%), Str. agalactiae (5.8%), Staph. aureus (4.2%), Staph. intermedius (3.1%), Enterobacter sp. (1.5%), Klebsiella sp., E. coli (1.05%), Micrococcus sp. (1.05%) and Serratia marcescens (0.52%). Milk samples from every quarter of each cow were also subjected to 6 mastitis marker tests named Somatic cell count (SCC), California mastitis test (CMT), electrical conductivity (EC) by EC-meter as well as by hand-held mastitis detector, pH detection by impregnated paper strip and also by pH meter. Efficacy of mastitis markers for diagnosis of sub-clinical mastitis was determined by comparing results of mastitis marker tests with microbiological findings. Mean value of SSC in milk from healthy quarters was significantly lower (p≤ 0.01) than that in milk from infected quarters. Significantly higher (p≤ 0.01) value of SSC was observed in milk samples having coagulase positive staphylococci as compared to that in milk from quarter with coagulase negative pathogens. The mean electrical conductivity (EC) in milk samples from infected quarters was significantly higher (P<0.05) than that from healthy quarters. Numbers and percentages of samples showing true positive, true negative, false positive and false negative results with SSC, CMT, EC by EC-meter, EC by hand-held meter, pH by impregnated strips, pH by digital pH-meter tests were evaluated and compared. The sensitivity and specificity of impregnated pH paper strip, CMT, pH-meter test, SCC, electrical conductivity by EC-meter and the same by hand-held mastitis detector were evaluated The compatibility between the results of SCC, impregnated pH paper strip, CMT, EC-meter, pH-meter, hand-held mastitis detector and bacteriological culture examination (reference test) was found to be 64.4, 63.4, 61.5, 59, 59 and 53 respectively.