This study proposes a sensor-less adaptive fuel concentration control (SAFCC) algorithm to maintain methanol concentration consistency for direct methanol fuel cells (DMFC). Methanol concentration has a dominant effect on fuel cell performance, however varying load poses a problem to maintain consistent concentration. The transient response for varying load is influenced by a series of interactively complex factors. Here, we introduce the SAFCC algorithm by measuring the present voltage and checking the decrease from a reference voltage. Compared to existing literature on sensor-less control methods, the delicate but simple algorithm can avoid complex mathematical derivation while maintaining quick decision to inject fuel. This algorithm can be used under both of steady and dynamic loading conditions and has the adaptive capability suitable for degraded fuel cells. Practical experiments for several scenarios are carried out with satisfactory results. (C) 2012 Elsevier B.V. All rights reserved.