Close monitoring of renal function is mandatory in recently kidney transplanted patients to pick the graft rejection earliest. Serum creatinine is commonly used for monitoring of renal allograft function. Cystatin C is a 13 .3 KDA protein reflects the glomerular filtration rate independent of age, muscle mass, inflammation or liver disease, is recently proposed as an alternative marker of glomerular function. The diagnostic efficiency of Cystatin C is not well studied in recent renal Transplant patients. The present study was therefore undertaken. 25 recently renal transplanted patients from a referral hospital in Riyadh KSA, between Jan 2004 to June 2004 were followed from first day post transplant till discharge from hospital (10.4+4.25 days). Apart from patient’s demographics, height, weight, BMI, blood sugar, liver profile, and kidney profile were recorded. Serum Cystatin C was estimated by Particle Enhanced Nephro Immunoassay. This assay employs antibody coated latex particles which react with Cystatin C (antigen) in the specimen in a reaction cell of an automated nephlometer (Dade Behring Germany). While creatinine was measured by enzymatic method on Auto analyzer. 25 post renal transplant patients were followed for 10.46±4.25 days starting from first post transplant day. There were 7 (28%) males and 18 (72%) females. mean age was 41.7±11.9 (20-68yrs). Due to recovery of renal function both serum creatinine and Cystatin C were reduced from pre transplant higher levels towards normal levels in the post transplant period. The serum creatinine in the pre-transplant patients was 658.91±248.umolls /l (264, 8- 1195 mmols/l) .On the Day 1, serum creatinine was reduced by 67.8 ± 15.3 % (211±92 m mol/l) from its pre transplant level p=0.000. Similarly on the post transplant Day 1, serum Cystatin C was reduced by 68.96±22.8% from its pre transplant level. (From 7.6±3.09mg/l pretransplant to 1.73±0.63mg/l at day 1 post transplant) p=0.000. A greater reduction in serum Cystatin C level was noted in post transplant recovery phase than serum creatinine. On the Day 2, post transplant, serum creatinine was reduced by 71.4±21.5% from its pre transplant level, while on the Day2, serum Cystatin C was reduced by 72.16 ±19.44 % from its pre transplant level. A strong correlation was found between serum creatinine and serum Cyststin Cr = .604, p =.002. How ever the reduction in the serum Cystatin C was greater than serum creatinine. On the Day 3: serum Cystatin C was reduced by 71.36±18.7 %. A strong correlation was found on the Day 3 also between serum creatinine and serum Cystatin C r =.689, p =0.000.On the subsequent post transplant days similar parallel day to day variations were noted in serum creatinine and serum Cystatin C. Eight of renal transplant patients had delayed graft function recovery . In these patients also parallel reduction of serum levels of creatinine and Cystatin C was observed. On the day 10, serum creatinine was reduced by 82.2±7.02%, while serum Cystatin C was reduced by 82.1±1.9%. There was no difference between reduction of serum creatinine and serum Cystatin C p=0.969. Serum Cystatin C was not correlated with age or gender. In conclusion, serum Cystatin C goes parallel to serum Creatinine in day to day follow-up of post renal transplant patients. Strong correlation was found between serum creatinine and serum Cystatin C magnitude of change during graft function recovery was more with Cystatin C. Cystatin C can be used for the follow-up of post renal transplant patients. Being independent of age sex, inflammation and liver dysfunction it can prove to be better marker of renal function.