Human illnesses due to algal blooms (cyanobacterial toxins, or cyanotoxins) are under-recognized and underreported. Although humans normally avoid bloom waters, incidental and accidental exposures to cyanotoxins as well as outbreaks have been documented. Exposures to cyanotoxins may occur by ingestion, dermal contact, and inhalation. Freshwater cyanotoxins can have neurotoxic, hepatotoxic, nephrotoxic, and dermatoxic health effects in humans, pets, and farm animals. Cyanobacteria and their toxins can have a significant impact on the drinking and recreational water quality, aquatic ecosystems, and animals. Although great strides have been made in environmental, ecological, and chemical cyanotoxin research, epidemiological studies and surveillance have been hindered by the lack of definitive diagnostic tests. Reducing the risk of exposure to cyanotoxins is an effective measure to prevent illness. This chapter will discuss the common freshwater cyanobacterial toxins, the adverse human health effects that may be encountered, and recommendations healthcare practitioners can provide to prevent exposure for those in rural communities.