Three main types of creatinine potentiometric membrane sensors are described. They are based on the use of dibenzo-30-crown-10 (DB30C10) with potassium tetrakis(p-chlorophenyl)borate type (I), dibenzo-30-crown-10 alone type (II), and potassium tetrakis(p-chlorophenyl)borate alone type (III), incorporating in poly(vinyl chloride) matrix membrane plasticized with either o-nitrophenyl octyl ether or dioctylphthalate. The sensors are used for quantification of creatinine after soaking the membranes in 0.1 M creatinine solution for 2 days. The sensors show almost the same potentiometric response characteristics. Sensor type (I) exhibits Nernstian responses over a concentration range of 5.0 × 10−5 mol l−1–1.0 × 10−2 mol l−1 creatinine with cationic slopes of 59.5 ± 0.1 and 60 ± 0.2 mV decade−1 and detection limits of 1.1 × 10−5 mol l−1 and 8 × 10−6 mol l−1 creatinine, over the pH range of 3.5–6.5 and 3.5–7.0, for o-NPOE and DOP solvent mediators, respectively. Sensor type (II) displays Nernstian responses over a concentration range of 6.0 × 10−5 mol l−1–1.0 × 10−2 mol l−1 creatinine with cationic slopes of 60.0 ± 0.1 and 65.0 ± 0.2 mV decade−1 and detection limits of 1.5 × 10−5 mol l−1 and 1.4 × 10−5 mol l−1 creatinine over the pH range of 2.6–6.2 and 2.5–6.0, for o-NPOE and DOP solvent mediators, respectively. Sensor type (III) shows Nernstian responses over a concentration range of 7.0 × 10−5 mol l−1–1.0 × 10−2 mol l−1 creatinine with cationic slopes of 60 ± 0.1 and 62.0 ± 0.2 mV decade−1 and detection limits of 2.7 × 10−5 mol l−1 and 2.0 × 10−5 mol l−1 creatinine over the pH range of 2.5–6.0, for o-NPOE and DOP solvent mediators, respectively. The response times of the sensors for 10−3 mol l−1 creatinine solution are instantaneous (4–10 s). The sensors show long-term stability with life span of ∼6 months. The sensors are used for determination of serum creatinine of rats (Rattus Norvigicus) with mean R.S.D. of 2.62%, and the results agreed well with the Jaffe kinetic method.