The paper deals with continuous-time adaptive control of a nonlinear process. A nonlinear model of the process is approximated by a continuous-time external linear model. The parameters of the CT external linear model are estimated via parameters of a corresponding delta model. The control system configuration with two feedback controllers is considered. The controller design is based on the polynomial approach. The resulting proper controllers ensure stability of the control system as well as asymptotic tracking of the step reference and step load disturbance attenuation. The adaptive control is tested on a nonlinear system represented by a model of two funnel liquid tanks in series