We investigated whether patient disease characteristics can explain differences in patients registered at the psoriatic arthritis clinic before 1987 who were seen regularly (139, "regular") to those who had not been seen for 2 years before 1989 (165, "inactive"). Despite a higher percentage of women in the regular group (p = 0.0058), logistic regression analysis identified no significant differences in disease severity or treatment at the first or last assessment before 1987. A followup study in 1989 revealed that of the 165 inactive patients, 20 had died and 64 had moved away. Of the 81 remaining patients, 18 were not interested, 18 were seeing other physicians, and 45 returned for followup. The latter 45 patients were compared to 85 of the regular patients who were seen during the same period. Both groups demonstrated similar disease attributes at first and last assessments before 1987. At their 1989 assessments, the same degree of disease progression was noted in both groups. Thus, loss to to followup appears to be random, and should not influence further studies of these patients.