Introduction: Silica is used in many industries such as foundries, glass production, cement, concrete, ceramic, porcelain, pottery, bricks, sandblasting, abrasives and construction activities. Several studies have linked long term silica exposure to renal diseases, especially glomerulonephritis. Aim of Work: To study the effect of silica exposure on the renal functions among iron and steel foundry workers. Materials and Methods: Seventy workers exposed to silica in an iron and steel foundry in Helwan, Egypt, were compared to 40 non-exposed individuals as regards full medical and occupational histories, full clinical examination and laboratory investigations including measurement of serum creatinine, serum cystatin C, serum urea, urinary silica, urinary albumin and urinary α1-microglobulin. Albumin creatinine ratio (ACR) and estimated glomerular filtration rate (e-GFR) were also calculated. Results: A statistically significant higher values of urinary silica, urinary albumin, urinary α1-microglobulin, serum creatinine, serum cystatin C and ACR were detected among the exposed group compared to the control. A statistically significant lower value of e-GFR was found among the exposed group. Statistically significant positive correlations were present between duration of employment and each of urinary silica, serum cystatin C, serum creatinine, serum urea, urinary α1-microglobulin, urinary albumin and ACR levels among the exposed group. Statistically significant positive correlations were also detected between urinary silica level and each of serum cystatin C, serum creatinine, serum urea, urinary α1-microglobulin, urinary albumin and ACR among the exposed group. Whereas, the e-GFR showed statistically significant negative correlations with both duration of employment and the urinary silica level among the exposed group. Conclusion and Recommendations: Silica exposure was associated with altered kidney function tests and decreased level of the e-GFR. Pre-employment and periodic medical examinations for silica-exposed workers should include clinical examination and determination of kidney functions, e-GFR, urinary α1-microglobulin and serum.cystatin C for early detection of kidney affection