In this paper, the problem of fault detection filter design is dealt with for a class of switched positive systems with packet dropouts on the channel between the sensors and the filters. The phenomena of packet dropouts are governed by a Bernoulli process, and a stochastic switched positive system is established based on the augmented states of the plants and filters. Two criteria are developed to evaluate the performance of the fault detection for the system under investigation. Sufficient conditions are established on the existence of the desired filters for the mean-square stability with an L 1 disturbance attenuation level, and an index for the L fault sensitivity is also derived through constructing a switched Lyapunov function in term of linear programming. Two illustrative examples, one of which is concerned with the Leslie matrix model, are provided to show the effectiveness and applicability of the proposed results. well as parameter uncertainties. Accordingly, some relevant results have been reported [11,17,18], where the main idea is to transform the FD problem into an H =H 1 or H 1 filtering problem [15,[18][19][20]. This idea has recently been extended to switched positive systems. For example, an L 1filtering design problem for a continuous-time switched positive delay system has been studied in [16], and the fault detection of positive switched systems with time-varying delay has been achieved by designing a mixed L =L 1 observer via the delta operator approach in [17].On the other hand, in the transmission and processing of measurement data from the sensors to the filter/estimator/detector, the packet dropout (or missing measurements) is usually unavoidable due mainly to the limited bandwidth of the channels and temporal sensor failures. Clearly, the packet dropout would degrade the system performance, and its impact on the fault detection problem has been an emerging challenging problem [21]. So far, a common approach to modelling the packet dropouts has been the use of a random variable satisfying the Bernoulli binary distribution taking values on either 1 or 0, where 1 implies the perfect signal delivery, and 0 represents the packet dropout. The fault detection problem with packet dropouts has received considerable research attention, and many important results have been reported in recent years [13,[22][23][24]. In particular, such problem has been dealt within networked systems with distributed sensors [23]. To the best of the authors' knowledge, the FD problem for discrete-time switched positive systems with packet dropouts has not gained adequate attention yet, and this motivates the current investigation with hope to demonstrate the application potential in practical engineering.In this paper, the FD problem for switched positive systems subject to random packet dropouts is investigated, where the Bernoulli distributions are employed to describe the phenomena of the packet dropouts. When the packet dropout occurs, the data received at the last time instant is used for updating the filter ...