Forty two genotypes / varieties of tomato were evaluated for resistance to root knot nematode  Meloidogyne incognita (Kofoid & White) Chitwood under glasshouse conditions their response was studied in terms of root gall index and number of egg masses per plant. Among the genotypes 28 genotypes/varieties were found highly susceptible to M. incognita   having more than 30 galls/plant. Three genotypes viz., EC 135580, Cherry tomato (round) and cherry tomato (oval) showed moderate resistance with the number of galls from 11 to 20 per plant. Only one variety (Hisar Lalith) exhibited resistance response to root knot nematode with less number of galls per plant (<10 galls/plant). However, none was found highly resistant to root knot nematode, M. incognita. Spectrophotometer analysis showed higher total phenols (516.4), PAL (18.22) and oxidative enzymes viz., peroxidase (2.15) and polyphenol oxidase (2.37) activity in resistant genotypes than in susceptible genotypes. Among the genotypes tested Hisar Lalith registered higher phenol activity (516.4) compared to other genotypes inoculated with M. incognita. PAL is the most important enzyme in the synthesis of phenols, phytoalexin and lignin. The enzyme estimated in the present investigation showed that resistant genotypes possessed higher PAL activity than susceptible genotypes indicating the inherent higher content of PAL in resistant genotypes. In the present study, the plants inoculated with M. incognita showed a substantial rise in PO and PPO activity in both susceptible and resistant genotypes; however the activity was more in resistant genotypes.