In this thesis, chemiluminescence (CL) method was used for the determination of some drugs including; cysteine, noscapine, enrofloxacin, phenothiazines such as perphenazine, promazine, chlorpromazine and flupheniazine. Moreover a CL method was proposed for the simultaneous determination of codeine and noscapine. In these methods the compounds were determined using [Ru(phen) 3 ] +2 -Ce(IV) CL system. For the determination of cysteine, this compound was injected into a flow containing a mixture of Ce(IV) and Ru(II) complex. Cysteine can reduce produced Ru(III) and convert it to Ru(II). A fraction of reproduced Ru(II) is in its excited state and can emit light. The method has a relatively good detection limit (0.7×10 -7 mol/L) and linear dynamic range (0.8×10 -7 -1.0×10 -3 mol/L). Noscapine can be detected by the proposed CL method mentioned above. In the this method, linear range and detection limit for noscapine are 3.0×10 -7 -1.0×10 -4 mol/L and 0.7×10 -8 mol/L respectively. We also proposed the first CL method for the determination of enrofloxacin. Its therapeutic concentration in blood serum of many animals is in the range 0.1-0.8 µg/mL. In this method a good sensitivity was obtained (detection limit of 0.003 µg/mL) for enrofloxacin. In this research, optimization of experimental variables were performed using multivariate methodology and experimental design. The results were four times better than one at a time procedure. Linear dynamic range and relative standard deviation (RSD% for concentration of 0.14 µg/mL) were 0.008-3.360 µg/mL and 4.2%, respectively. In this thesis also a new CL method proposed for the determination of some phenothiazines including: perphenazine, promazine, chlorpromazine and fluphenazine. In the proposed method, optimization of some variables performed using experimental design. With respect to low detection limit and therapeutic and toxic dosage of these drugs, they can be determined in human serum. Their detection limits are 0.4×10 -3 , 0.012, 0.020 and 0.015 µg/mL and their linear dynamic ranges are 1.0×10 -3 -1.3, 0.020-32.000, 0.030-36.000 and 0.030-20.000 for perphenazine, promazine, chlorpromazine and flupheniazine respectively.Simultaneous determination of compounds by CL methods has not been any remarkable improve up to now. In this thesis a new method proposed for the simultaneous determination of codeine and noscapine. In this method a three dimension data matrix was constructed and an n-way method ( N -PLS) was used for the modeling. After validating the model, it was employed for simultaneous determination of codeine and noscapine in pharmaceuticals. Recovery percentages were in the range 90-110% for studied alkaloids.