Traditional control charts for process monitoring are based on taking samples from the process at fixed length sampling intervals. More recently, research works focused on the use of variable sampling intervals (VSIs), where the lengths of the sampling intervals are varied according to the process quality. A short sampling interval is considered when the process quality indicates a possible out-of-control situation while a long sampling interval is considered, otherwise. In this paper, the VSI run sum (RS) View the MathML source chart is proposed with its optimal scores and parameters determined using an optimization technique to minimize the out-of-control average time to signal (ATS) or the adjusted average time to signal (AATS). A Markov-chain method is used to evaluate both the ATS and AATS of the proposed chart, for the zero and steady state cases, respectively. Results show that the VSI RS View the MathML source chart is considerably more efficient than the basic RS View the MathML source chart. The VSI RS View the MathML source chart performs generally well compared with other competing charts, such as the standard View the MathML source, synthetic View the MathML source, exponentially weighted moving average (EWMA) View the MathML source, VSI View the MathML source and VSI EWMA View the MathML source charts. The sensitivity of the VSI RS View the MathML source chart can be enhanced further by adding more scoring regions or a head-start feature. An illustrative example is presented to explain the implementation of the proposed VSI RS View the MathML source chart.