A number of polysiloxanes and their copolymers were synthesized by hydrolytic polycondensation of dialkyl (ary) dichlorosilane or their mixtures in a saturated solution of NaCl in water at low temperature (0-5 degrees C). These polysiloxanes were characterized by intrinsic viscosity, infrared and nuclear magnetic resonance spectroscopy. 2-Pyridine aldoxime-chloride (PAM-Cl) was incorporated into these polysiloxanes, followed by crosslinking with tetraethoxysilane using dibutyltindilaurate as catalyst. The effect of pH on in vitro release rate of PAM-Cl from polysiloxane matrices was investigated in phosphate buffer of pH 3.0, 7.4, and 10.0 at 37 degrees C using an ultraviolet spectrophotometer. Transport parameters like the order of release and diffusion coefficients for these systems (polysiloxane-PAM-Cl) were also calculated.