This Alert was issued to inform farm workers and owners about the dangers of manure pits where oxygen deficient, toxic and/or explosive atmospheres often result from fermentation of the wastes in confined areas. Seven deaths are described in this report. In each case the worker suffocated after entering manure pits. Two incidents were responsible for the 7 deaths. The four potentially dangerous gases found in these pits include methane (74828), hydrogen-sulfide (7783064), carbon-dioxide (124389), and ammonia (7664417). From 1980 through 1985 16 deaths resulted from the suffocation of workers in manure pits or similar waste tanks. In the first case presented, a 31 year old male dairy farmer and his 33 year old brother died after entering a 25 foot square, 4.5 foot deep manure pit inside a building on their farm. A pump intake pipe in the pit had clogged and the farmer descended into the pit to clear the obstruction. He collapsed and the brother entered the pit to rescue him. In the second case report five farm workers died after consecutively entering a manure pit on their farm. The pit measured 20 by 24 feet and was 10 feet deep. NIOSH recommends that manure pits on farms be treated like any other type of confined space. This involves providing proper ventilation, testing the atmosphere before entry, having a standby person present and in contact with the worker entering the pit, and using a safety belt or harness with a lifeline tied to mechanical lifting equipment (winch, hoist, or pulley).