Leucopenia is one of the most worrying of the many toxic effects of second-line drug therapy for rheumatoid arthritis, and much time and energy is expended in screening for it. Sulphasalazine (SASP) is generally claimed to be safer than some alternative second-line drugs but the reported incidence of leucopenia has varied widely. We have examined, retrospectively, all records of blood counts before, during and after treatment in 326 SASP treated patients and in 213 on gold. Leucopenia on at least one occasion occurred in up to 10% of patients on both drugs but usually recovered spontaneously in spite of continued therapy. 'Serious' leucopenia leading directly to drug withdrawal was a rare event occurring in only one SASP patient and in two patients receiving gold treatment. Most episodes of leucopenia do not require drug withdrawal and may not be drug related.