The camp was built, managed and supervised by Department III of the "Ustaška Narodna Služba" or "UNS" (lit. "Ustaše People's Service"), a special police force of the ISC. Vjekoslav "Maks" Luburić was head of the UNS. At different times, Miroslav Majstorović and Dinko Šakić managed the camp.
The Ustaše interned, tortured and executed men, women and children in Jasenovac. The largest number of victims were Serbs, but other victims included Jews, Bosnian Muslims, Gypsies, and Croatian resistance members opposed to the ISC regime. When they got to the camp, the prisoners were marked with colors: blue for Serbs, and red for "communists" (non-Serbian resistance members). Gypsies had no marks (this was later changed).
Most people who were sent to Jasenovac were killed at execution sites near the camp: Granik, Gradina, and other places. Prisoners who were kept alive were mostly people who had special skills (for example, doctors, pharmacists, electricians, shoemakers, and goldsmiths). They were forced to work at Jasenovac.
The living conditions in the camp were terrible, as was usual for Nazi death camps. Prisoners were fed very little, not given enough clothing or shelter to stay warm, had no health care, and were abused by the Ustaše guards. Also, as in many camps, conditions would be improved temporarily when special groups visited. For example, when members of the press visited in February 1942, and later when a Red Cross delegation visited in June 1944, the prisoners were treated better until the visitors left. Then the living conditions would go back to usual.
Like at all Nazi death camps, the food given to prisoners at Jasenovac was not enough to keep them alive. The kind of food they were given changed over time. In camp Brocice, inmates were given a "soup" made of hot water with starch for breakfast, and beans for lunch and dinner. (These "meals" were served at 6:00, 12:00 and 21:00.) Food in Camp No. III was better at first, with potatoes instead of beans. However, in January, prisoners started getting only one daily serving of thin "turnip soup". By the end of the year, the diet had been changed again, to three daily portions of thin gruel made of water and starch. More changes were made, but prisoners never got enough food to keep them from starving.
The water at Jasenovac was even worse than at most death camps. There was no clean water at the camp. Prisoners were forced to drink water from the Sava River, which was contaminated with "hren" (horseradish).
In the first camps, Brocice and Krapje, inmates slept in regular concentration-camp barracks. These were made of wood and had three tiers (levels) of bunks.
In Camp No. III, which housed about 3,000 prisoners, there was not enough shelter for everyone. At first, inmates slept in the attics of the camp's workshops, in an open depot used as a railway "tunnel", or simply outside in the open. A short time later, eight barracks were built. Inmates slept in six of these barracks. The other two were used as a "clinic" and a "hospital." These were not places where inmates could get medical treatment and get better. They were places where sick inmates were put together to die or be killed.
As in all concentration camps, prisoners at Jasenovac had to work about 11 hours a day. They did hard, forced labor, and were always watched by the Ustaše guards. These guards would execute inmates even for small reasons, and say the inmates were "sabotaging labor."
Ustasas Hinko Dominik Picilli and Tihomir Kordić controlled the labor section. Picilli would personally whip inmates to make them work harder. He divided the "Jasenovac labor force" into 16 groups, including groups of construction workers, brick-workers, metal-works, and agricultural workers. Many inmates died from the hard work. Brick-working was especially hard and dangerous. Inmates working as blacksmiths were forced to make knives and other weapons for the Ustaše. Building dikes was the most feared job of all.
Inside the camp, there was no sanitation. Prisoners had no way to keep things clean, and had to live in terrible conditions. Blood, vomit and dead bodies filled the barracks. The barracks were also full of pests like lice and rats, which spread disease. The barracks smelled terrible because inmates had to use a bucket for a toilet during the evenings. The bucket often spilled.
During breaks from work (from 5:00-6:00; 12:00-13:00, and 17:00-20:00), inmates were allowed to empty their bowels in public latrines. These were big pits that lay bare in the open field, covered with planks of wood. Inmates often fell inside and died. The Ustaše encouraged this by having prisoners separate the planks. Sometimes, the Ustaše would even drown inmates inside the pits. When it rained, these pits would overflow and drain into the lake. This meant that urine and feces would mix into the water which the prisoners had to drink.
Inmates were given rags and blankets, but they were very thin. The barracks were also not enough to keep inmates warm from the cold. Prisoners' clothes and blankets were rarely cleaned. Inmates were allowed to wash them quickly in the lake once a month, except during the winter, when the lake froze. Then, inmates were sometimes allowed to boil a few clothes, but not well enough to get them clean.
Because of these terrible living conditions, inmates suffered from illnesses that led to epidemics of typhus, typhoid, malaria, lung infections, influenza, dysentery, and diphtheria.
The Ustaše took away all of the inmates' clothes and other things. They were given only prison uniforms, made out of rags. In winter, inmates were given thin "rain-coats," and they were allowed to make light sandals. Inmates were given a small personal food bowl, to hold the 0.4 litres of "soup" they were fed. An inmate whose bowl was missing (because another inmate had stolen it to use it as a toilet) would get no food.
During delegation visits, inmates were given bowls twice as large as usual, with spoons. Also, during these visits, inmates were given colored tags.
Prisoners were affected by a constant fear of death, and terrible stress of being in a situation in which the living and dead are very close together.
When they first arrived at the camp, inmates would be shocked by the terrible conditions on the trip to the camp, and in the camp itself. The Ustaše would increase this shock by murdering a number of inmates as soon as they got to the camp, and by temporarily housing new-arrivals in warehouses, attics, in the train tunnel and outdoors.
After the inmates grew familiar with life in camp, they would have to get used to living through the hardships, abuse, torture, and deaths of other prisoners. The danger of death was greatest during "public performances for public punishment," also called selections. Inmates would be lined up in groups, and individuals would be randomly pointed out to be killed while facing the rest. The Ustaše would make this worse by making the process take a long time. They would walk around and ask questions; gaze at inmates; choose one person, then change their mind and choose another.
Inmates reacted to being in Jasenovac in two basic ways. Some became activists. They formed resistance movements (groups who tried to fight the Ustaše in different ways, like stealing food, planning escapes and revolts, and trying to get in touch with people outside the camp). But most of the inmates reacted by just trying to survive, and get through the day unharmed. This was not "going in line to slaughter," but rather another strategy to try to survive.