Some people believe that certain issues should be protected from all trade-offs. These issues are referred to as "protected values." We investigated whether some patients with rheumatoid arthritis (RA) treat the risk of adverse effects (AE) as "protected values," i.e., as unacceptable regardless of how small the risk. Patients with RA rated willingness to risk 17 different AE on a visual analog scale, where 0 = not willing under any circumstances and 100 = definitely willing. Participants then rated willingness to take medication as the risk of each AE was progressively decreased by 2 levels from its actual risk, using a 5 level scale ranging from 10 in 100 to 1 in 100,000. Between 32% and 39% of participants were not more willing to accept a risk of AE causing reversible cosmetic changes (e.g., acne), between 35% and 47% were not more willing to accept a risk of AE causing reversible discomfort (e.g., rash), and between 41% and 45% were not more willing to accept a risk of AE causing potential irreversible damage (e.g., pneumonitis) as the probability of each of these AE was substantially decreased. Unwillingness to accept risk of toxicity was especially evident for cancer, where 66% of patients refused to accept a risk of cancer occurring in 1 in 100,000 persons. Among patients particularly concerned with the risk of drug toxicity, many remain unwilling to accept the risk of AE even when their probability is decreased to levels far below their actual risk. These results suggest that patients may treat particularly worrisome AE as protected values, which may lead to poor decision-making in clinical practice.